Effects of detector dead-time on quantitative analyses involving boron and multi-hit detection events in atom probe tomography.

PubMed

Meisenkothen, Frederick; Steel, Eric B; Prosa, Ty J; Henry, Karen T; Prakash Kolli, R

2015-12-01

In atom probe tomography (APT), some elements tend to field evaporate preferentially in multi-hit detection events. Boron (B) is one such element. It is thought that a large fraction of the B signal may be lost during data acquisition and is not reported in the mass spectrum or in the 3-D APT reconstruction. Understanding the relationship between the field evaporation behavior of B and the limitations for detecting multi-hit events can provide insight into the signal loss mechanism for B and may suggest ways to improve B detection accuracy. The present work reports data for nominally pure B and for B-implanted silicon (Si) (NIST-SRM2137) at dose levels two-orders of magnitude lower than previously studied by Da Costa, et al. in 2012. Boron concentration profiles collected from SRM2137 specimens qualitatively confirmed a signal loss mechanism is at work in laser pulsed atom probe measurements of B in Si. Ion correlation analysis was used to graphically demonstrate that the detector dead-time results in few same isotope, same charge-state (SISCS) ion pairs being properly recorded in the multi-hit data, explaining why B is consistently under-represented in quantitative analyses. Given the important role of detector dead-time as a signal loss mechanism, the results from three different methods of estimating the detector dead-time are presented. The findings of this study apply to all quantitative analyses that involve multi-hit data, but the dead-time will have the greatest effect on the elements that have a significant quantity of ions detected in multi-hit events. Published by Elsevier B.V.

Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields.

PubMed

Zhu, Wuming; Trickey, S B

2017-12-28

In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li + , Be + , and B + , in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B field.

Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields

NASA Astrophysics Data System (ADS)

Zhu, Wuming; Trickey, S. B.

2017-12-01

In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li+, Be+, and B+, in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B field.

Operation of Lanzhou all permanent electron cyclotron resonance ion source No. 2 on 320 kV platform with highly charged ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, W., E-mail: luwang@impcas.ac.cn; University of Chinese Academy of Sciences, Beijing 100049; Li, J. Y.

2014-02-15

The 320 kV platform for multi-discipline research with highly charged ions is a heavy ion beam acceleration instrument developed by Institute of Modern Physics, which is dedicated to basic scientific researches such as plasma, atom, material physics, and astrophysics, etc. The platform has delivered ion beams of 400 species for 36 000 h. The average operation time is around 5000 h/year. With the beams provided by the platform, lots of outstanding progresses were made in various research fields. The ion source of the platform is an all-permanent magnet electron cyclotron resonance ion source, LAPECR2 (Lanzhou All Permanent ECR ion source No.more » 2). The maximum axial magnetic fields are 1.28 T at injection and 1.07 T at extraction, and the radial magnetic field is up to 1.21 T at the inner wall of the plasma chamber. The ion source is capable to produce low, medium, and high charge state gaseous and metallic ion beams, such as H{sup +}, {sup 40}Ar{sup 8+}, {sup 129}Xe{sup 30+}, {sup 209}Bi{sup 33+}, etc. This paper will present the latest result of LAPECR2 and the routine operation status for the high voltage platform.« less

Effects of Ion Atomic Number on Single-Event Gate Rupture (SEGR) Susceptibility of Power MOSFETs

NASA Technical Reports Server (NTRS)

Lauenstein, Jean-Marie; Goldsman, Neil; Liu, Sandra; Titus, Jeffrey L.; Ladbury, Raymond L.; Kim, Hak S.; Phan, Anthony M.; LaBel, Kenneth A.; Zafrani, Max; Sherman, Phillip

2012-01-01

The relative importance of heavy-ion interaction with the oxide, charge ionized in the epilayer, and charge ionized in the drain substrate, on the bias for SEGR failure in vertical power MOSFETs is experimentally investigated. The results indicate that both the charge ionized in the epilayer and the ion atomic number are important parameters of SEGR failure. Implications on SEGR hardness assurance are discussed.

Dipole-Guided Electron Capture Causes Abnormal Dissociations of Phosphorylated Pentapeptides

NASA Astrophysics Data System (ADS)

Moss, Christopher L.; Chung, Thomas W.; Wyer, Jean A.; Nielsen, Steen Brøndsted; Hvelplund, Preben; Tureček, František

2011-04-01

Electron transfer and capture mass spectra of a series of doubly charged ions that were phosphorylated pentapeptides of a tryptic type (pS,A,A,A,R) showed conspicuous differences in dissociations of charge-reduced ions. Electron transfer from both gaseous cesium atoms at 100 keV kinetic energies and fluoranthene anion radicals in an ion trap resulted in the loss of a hydrogen atom, ammonia, and backbone cleavages forming complete series of sequence z ions. Elimination of phosphoric acid was negligible. In contrast, capture of low-energy electrons by doubly charged ions in a Penning ion trap induced loss of a hydrogen atom followed by elimination of phosphoric acid as the dominant dissociation channel. Backbone dissociations of charge-reduced ions also occurred but were accompanied by extensive fragmentation of the primary products. z-Ions that were terminated with a deaminated phosphoserine radical competitively eliminated phosphoric acid and H2PO4 radicals. A mechanism is proposed for this novel dissociation on the basis of a computational analysis of reaction pathways and transition states. Electronic structure theory calculations in combination with extensive molecular dynamics mapping of the potential energy surface provided structures for the precursor phosphopeptide dications. Electron attachment produces a multitude of low lying electronic states in charge-reduced ions that determine their reactivity in backbone dissociations and H- atom loss. The predominant loss of H atoms in ECD is explained by a distortion of the Rydberg orbital space by the strong dipolar field of the peptide dication framework. The dipolar field steers the incoming electron to preferentially attach to the positively charged arginine side chain to form guanidinium radicals and trigger their dissociations.

Tailoring Ion Charge State Distribution in Tetramethyltin Clusters under Influence of Moderate Intensity Picosecond Laser Pulse: Role of Laser Wavelength and Rate of Energy Deposition

NASA Astrophysics Data System (ADS)

Sharma, Pramod; Das, Soumitra; Vatsa, Rajesh K.

2017-07-01

Systematic manipulation of ionic-outcome in laser-cluster interaction process has been realized for studies carried out on tetramethyltin (TMT) clusters under picosecond laser conditions, determined by choice of laser wavelength and intensity. As a function of laser intensity, TMT clusters exhibit gradual enhancement in overall ionization of its cluster constituents, up to a saturation level of ionization, which was distinct for different wavelengths (266, 355, and 532 nm). Simultaneously, systematic appearance of higher multiply charged atomic ions and shift in relative abundance of multiply charged atomic ions towards higher charge state was observed, using time-of-flight mass spectrometer. At saturation level, multiply charged atomic ions up to (C2+, Sn2+) at 266 nm, (C4+, Sn4+) at 355 nm, and (C4+, Sn6+) at 532 nm were detected. In addition, at 355 nm intra-cluster ion chemistry within the ionized cluster leads to generation of molecular hydrogen ion (H2 +) and triatomic molecular hydrogen ion (H3 +). Generation of multiply charged atomic ions is ascribed to efficient coupling of laser pulse with the cluster media, facilitated by inner-ionized electrons produced within the cluster, at the leading edge of laser pulse. Role of inner-ionized electrons is authenticated by measuring kinetic energy distribution of electrons liberated upon disintegration of excessively ionized cluster, under the influence of picosecond laser pulse.

Shaping of nested potentials for electron cooling of highly-charged ions in a cooler Penning trap

NASA Astrophysics Data System (ADS)

Paul, Stefan; Kootte, Brian; Lascar, Daniel; Gwinner, Gerald; Dilling, Jens; Titan Collaboration

2016-09-01

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) is dedicated to mass spectrometry and decay spectroscopy of short-lived radioactive nuclides in a series of ion traps including a precision Penning trap. In order to boost the achievable precision of mass measurements TITAN deploys an Electron Beam Ion Trap (EBIT) providing Highly-Charged Ions (HCI). However, the charge breeding process in the EBIT leads to an increase in the ion bunch's energy spread which is detrimental to the overall precision gain. To reduce this effect a new cylindrical Cooler PEnning Trap (CPET) is being commissioned to sympathetically cool the HCI via a simultaneously trapped electron plasma. Simultaneous trapping of ions and electrons requires a high level of control over the nested potential landscape and sophisticated switching schemes for the voltages on CPET's multiple ring electrodes. For this purpose, we are currently setting up a new experimental control system for multi-channel voltage switching. The control system employs a Raspberry Pi communicating with a digital-to-analog board via a serial peripheral interface. We report on the implementation of the voltage control system and its performance with respect to electron and ion manipulation in CPET. University of British Columbia, Vancouver, BC, Canada.

Laboratory Studies of Thermal Energy Charge Transfer of Silicon and Iron Ions in Astrophysical Plasmas

NASA Technical Reports Server (NTRS)

Kwong, Victor H. S.

1996-01-01

Charge transfer at electron-volt energies between multiply charged atomic ions and neutral atoms and molecules is of considerable importance in astrophysics, plasma physics, and in particular, fusion plasmas. In the year covered by this report, several major tasks were completed. These include: (1) the re-calibration of the ion gauge to measure the absolute particle densities of H2, He, N2, and CO for our current measurements; (2) the analysis of data for charge transfer reactions of N(exp 2 plus) ion and He, H2, N2, and CO; (3) measurement and data analysis of the charge transfer reaction of (Fe(exp 2 plus) ion and H2; (4) charge transfer measurement of Fe(exp 2 plus) ion and H2; and (5) redesign and modification of the ion detection and data acquisition system for the low energy beam facility (reflection time of flight mass spectrometer) dedicated to the study of state select charge transfer.

Modeling Solar Wind Flow with the Multi-Scale Fluid-Kinetic Simulation Suite

DOE PAGES

Pogorelov, N.V.; Borovikov, S. N.; Bedford, M. C.; ...

2013-04-01

Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) is a package of numerical codes capable of performing adaptive mesh refinement simulations of complex plasma flows in the presence of discontinuities and charge exchange between ions and neutral atoms. The flow of the ionized component is described with the ideal MHD equations, while the transport of atoms is governed either by the Boltzmann equation or multiple Euler gas dynamics equations. We have enhanced the code with additional physical treatments for the transport of turbulence and acceleration of pickup ions in the interplanetary space and at the termination shock. In this article, we present themore » results of our numerical simulation of the solar wind (SW) interaction with the local interstellar medium (LISM) in different time-dependent and stationary formulations. Numerical results are compared with the Ulysses, Voyager, and OMNI observations. Finally, the SW boundary conditions are derived from in-situ spacecraft measurements and remote observations.« less

Solar Wind Charge Exchange Studies Of Highly Charged Ions On Atomic Hydrogen

NASA Astrophysics Data System (ADS)

Draganić, I. N.; Seely, D. G.; McCammon, D.; Havener, C. C.

2011-06-01

Accurate studies of low-energy charge exchange (CX) are critical to understanding underlying soft X-ray radiation processes in the interaction of highly charged ions from the solar wind with the neutral atoms and molecules in the heliosphere, cometary comas, planetary atmospheres, interstellar winds, etc.. Particularly important are the CX cross sections for bare, H-like, and He-like ions of C, N, O and Ne, which are the dominant charge states for these heavier elements in the solar wind. Absolute total cross sections for single electron capture by H-like ions of C, N, O and fully-stripped O ions from atomic hydrogen have been measured in an expanded range of relative collision energies (5 eV/u-20 keV/u) and compared to previous H-oven measurements. The present measurements are performed using a merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source installed on a high voltage platform at the Oak Ridge National Laboratory. For the collision energy range of 0.3 keV/u-3.3 keV/u, which corresponds to typical ion velocities in the solar wind, the new measurements are in good agreement with previous H-oven measurements. The experimental results are discussed in detail and compared with theoretical calculations where available.

Relativistic Collisions of Highly-Charged Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ionescu, Dorin; Belkacem, Ali

1998-11-19

The physics of elementary atomic processes in relativistic collisions between highly-charged ions and atoms or other ions is briefly discussed, and some recent theoretical and experimental results in this field are summarized. They include excitation, capture, ionization, and electron-positron pair creation. The numerical solution of the two-center Dirac equation in momentum space is shown to be a powerful nonperturbative method for describing atomic processes in relativistic collisions involving heavy and highly-charged ions. By propagating negative-energy wave packets in time the evolution of the QED vacuum around heavy ions in relativistic motion is investigated. Recent results obtained from numerical calculations usingmore » massively parallel processing on the Cray-T3E supercomputer of the National Energy Research Scientific Computer Center (NERSC) at Berkeley National Laboratory are presented.« less

Recent Development of IMP LECR3 Ion Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Z.M.; Zhao, H.W.; Li, J.Y.

2005-03-15

18GHz microwave has been fed to the LECR3 ion source to produce intense highly charged ion beams although this ion source was designed for 14.5GHz. Then 1.1 emA Ar8+ and 325 e{mu}A Ar11+ were obtained at 18GHz. During the source running for atomic physics experiment, some higher charge state ion beams such as Ar17+ and Ar18+ were detected and have been validated by atomic physics method. Furthermore, a few special gases, e.g. SiH4 and SF6, were tested on LECR3 ion source to produce required ion beams to satisfy the requirements of atomic physics experiments.

Excited State Atom-Ion Charge-Exchange

NASA Astrophysics Data System (ADS)

Li, Ming; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana

2017-04-01

We theoretically investigate the exothermic charge-exchange reaction between an excited atom and a ground-state positive ion. In particular, we focus on MOT-excited Ca*(4s4p 1P) atoms colliding with ground-state Yb+ ions, which are under active study by the experimental group of E. Hudson at UCLA. Collisions between an excited atom and an ion are guided by two major contributions to the long-range interaction potentials, the induction C4 /R4 and charge-quadrupole C3 /R3 potentials, and their coupling by the electron-exchange interaction. Our model of these forces leads to close-coupling equations for multiple reaction channels. We find several avoided crossings between the potentials that couple to the nearby asymptotic limits of Yb*+Ca+, some of which can possibly provide large charge exchange rate coefficients above 10-10 cm3 / s. We acknowledge support from the US Army Research Office, MURI Grants W911NF-14-1-0378 and the US National Science Foundation, Grant PHY-1619788.

A facility to produce an energetic, ground state atomic oxygen beam for the simulation of the Low-Earth Orbit environment

NASA Technical Reports Server (NTRS)

Ketsdever, Andrew D.; Weaver, David P.; Muntz, E. P.

1994-01-01

Because of the continuing commitment to activity in low-Earth orbit (LEO), a facility is under development to produce energetic atmospheric species, particularly atomic oxygen, with energies ranging from 5 to 80 eV. This relatively high flux facility incorporates an ion engine to produce the corresponding specie ion which is charge exchanged to produce a neutral atomic beam. Ion fluxes of around 10(exp 15) sec(exp -1) with energies of 20-70 eV have been achieved. A geometrically augmented inertially tethered charge exchanger (GAITCE) was designed to provide a large column depth of charge exchange gas while reducing the gas load to the low pressure portion of the atomic beam facility. This is accomplished using opposed containment jets which act as collisional barriers to the escape of the dense gas region formed between the jets. Leak rate gains to the pumping system on the order of 10 were achieved for moderate jet mass flows. This system provides an attractive means for the charge exchange of atomic ions with a variety of gases to produce energetic atomic beams.

Slow Collisions of Si3+ with Atomic Hydrogen

NASA Astrophysics Data System (ADS)

Joseph, D. C.; Gu, J.-P.; Saha, B. C.; Liebermann, H. P.; Funke, P.; Buenker, R. J.

2010-03-01

Low energy electron capture from hydrogen atom by multi-charged ions continues to be of interest and applications include both magnetically confined fusion and astrophysical plasmas. The charge exchange process reported here, Si^3+ + H -> Si^2+ + H^+ is an important destruction mechanism of Si^3+ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si^3+, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the full quantum [1] and semi-classical molecular orbital close coupling (MOCC) [2] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states of and symmetry are calculated wing the MRD-CI package [3]. Details will be presented at the conference. [4pt] [1] L. B. Zhao, D. C. Joseph, B. C. Saha, H. P. Liebermann, P. Funke and R. J. Buenker, Phys. Rev A, 79, 034701 (1009).[0pt] [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990).[0pt] [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam) p 17.

Charge exchange in slow collisions of Si3+ with H

NASA Astrophysics Data System (ADS)

Joseph, D. C.; Saha, B. C.

2010-10-01

Low energy electron capture from atomic hydrogen by multi-charged ions continues to be of interest and has wide applications including both magnetically confined^ fusion and astrophysical plasmas. The charge exchange process reported here, Si^3+ + H -- Si^2+ + H^+ is an important destruction mechanism of Si^3+ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si^3+, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the semi-classical molecular orbital close coupling (MOCC) [1] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states are calculated using the MRD-CI package [2]. Details will be presented at the conference. [1] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990). [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry'' 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam) p 17.

Charged-particle stereotactic radiosurgery

NASA Astrophysics Data System (ADS)

Lyman, John T.; Fabrikant, Jacob I.; Frankel, Kenneth A.

1985-05-01

Charged-particle stereotactic radiosurgery is the technique of using accelerated atomic nuclei for the irradiation of a small volume target to a high dose in a short time interval. This is contrasted with conventional radiotherapy where large volumes are treated with many small fractions of photon or electron radiation over a multi-week period. The helium-ion beam used for charged-particle stereotactic radiosurgery at the Lawrence Berkeley Laboratory 184-inch Synchrocyclotron is described. This beam is being used for the treatment of inoperable, deep, intracranial arteriovenous malformations (AVMs). Intracranial AVMs are collections of abnormal blood vessels in the brain that may represent a failure of vessels to mature properly and after a long period of slow growth they may produce clinically recognizable neurological symptoms. Based on our experience using narrow beams of helium ions for stereotactic radiosurgical treatment of AVM patients, the characteristics of the treatments are described. Improvements to the technique which are possible by the use of other charged particle beams are discussed.

Analysis of spectra of 3s-3p and 3p-3d transitions of highly-charged copper ions

NASA Astrophysics Data System (ADS)

Su, M. G.; Min, Q.; He, S. Q.; Wu, L.; Sun, R.; Ding, X. B.; Sun, D. X.

2017-08-01

Beam-foil excited spectra in the range of 160-360 Å from highly charged copper ions were identified with the aid of the National Institute of Standards and Technology Atomic Spectra Database and theoretical calculations with Cowan and Flexible Atomic Code (FAC) calculations. Spectra arising from 3s-3p and 3p-3d transitions of Cu13+-Cu22+ ions were considered. The ion fraction at an ion beam energy of 110 MeV was estimated from the equilibrium charge distribution of the fast ion beams after passing through the solid. The corresponding simulated spectra were in good agreement with the experimental result. Our Cowan and FAC calculation results should be useful for further spectral identification and lifetime measurements of highly charged copper ions.

Charge transfer in ultracold gases via Feshbach resonances

NASA Astrophysics Data System (ADS)

Gacesa, Marko; Côté, Robin

2017-06-01

We investigate the prospects of using magnetic Feshbach resonance to control charge exchange in ultracold collisions of heteroisotopic combinations of atoms and ions of the same element. The proposed treatment, readily applicable to alkali or alkaline-earth metals, is illustrated on cold collisions of +9Be and 10Be. Feshbach resonances are characterized by quantum scattering calculations in a coupled-channel formalism that includes non-Born-Oppenheimer terms originating from the nuclear kinetic operator. Near a resonance predicted at 322 G, we find the charge exchange rate coefficient to rise from practically zero to values greater than 10-12cm3 /s. Our results suggest controllable charge exchange processes between different isotopes of suitable atom-ion pairs, with potential applications to quantum systems engineered to study charge diffusion in trapped cold atom-ion mixtures and emulate many-body physics.

An estimating formula for ion-atom association rates in gases

NASA Technical Reports Server (NTRS)

Chatterjee, B. K.; Johnsen, R.

1990-01-01

A simple estimating formula is derived for rate coefficients of three-body ion atom association in gases and compare its predictions to experimental data on ion association and three-body radiative charge transfer reactions of singly- and doubly-charged rare-gas ions. The formula appears to reproduce most experimental data quite well. It may be useful for estimating the rates of reactions that have not been studied in the laboratory.

Charge exchange molecular ion source

DOEpatents

Vella, Michael C.

2003-06-03

Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

Final Technical Report of Project DE-FG02-96ER14647

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lundeen, Stephen R.

This is the final technical report of work completed under DOE support over the period Sept. 1, 1996 until May 31, 2015. The title of the project was "Ion/Excited Atom Collision Studies with a Rydberg Target and a CO2 Laser" from 9/1/96 to 10/31/06, and "Properties of Actinide Ions from Measurements of Rydberg Ion Fine Structure" from 11/1/06 until 5/31/15. The primary technical results were a detailed experimental study of resonant charge transfer between Rydberg atoms and highly-charged ions, and unique measurements of many properties of multiply-charged Thorium ions.

Genetics Home Reference: SLC4A1-associated distal renal tubular acidosis

MedlinePlus

... exchanger 1 (AE1) protein, which transports negatively charged atoms (anions) across cell membranes. Specifically, AE1 exchanges negatively charged atoms of chlorine (chloride ions) for negatively charged bicarbonate ...

Laboratory Measurements of Charge Transfer on Atomic Hydrogen at Thermal Energies

NASA Technical Reports Server (NTRS)

Havener, C. C.; Vane, C. R.; Krause, H. F.; Stancil, P. C.; Mroczkowski, T.; Savin, D. W.

2002-01-01

We describe our ongoing program to measure velocity dependent charge transfer (CT) cross sections for selected ions on atomic hydrogen using the ion-aloin merged-beams apparatus at Oak Ridge Natioiial Laboralory. Our focus is on those ions for which CT plays an important role in determining the ionization structure, line emis sion, and thermal structure of observed cosmic photoionized plasmas.

An analytic expression for the sheath criterion in magnetized plasmas with multi-charged ion species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatami, M. M., E-mail: m-hatami@kntu.ac.ir

2015-04-15

The generalized Bohm criterion in magnetized multi-component plasmas consisting of multi-charged positive and negative ion species and electrons is analytically investigated by using the hydrodynamic model. It is assumed that the electrons and negative ion density distributions are the Boltzmann distribution with different temperatures and the positive ions enter into the sheath region obliquely. Our results show that the positive and negative ion temperatures, the orientation of the applied magnetic field and the charge number of positive and negative ions strongly affect the Bohm criterion in these multi-component plasmas. To determine the validity of our derived generalized Bohm criterion, itmore » reduced to some familiar physical condition and it is shown that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when entrance velocity of ion into the sheath satisfies the obtained Bohm criterion. Also, as a practical application of the obtained Bohm criterion, effects of the ionic temperature and concentration as well as magnetic field on the behavior of the charged particle density distributions and so the sheath thickness of a magnetized plasma consisting of electrons and singly charged positive and negative ion species are studied numerically.« less

Solar Wind Prediction at Pluto During the New Horizons Flyby: Results From a Two-Dimensional Multi-fluid MHD Model of the Outer Heliosphere

NASA Astrophysics Data System (ADS)

Zieger, B.; Toth, G.; Opher, M.; Gombosi, T. I.

2015-12-01

We adapted the outer heliosphere (OH) component of the Space Weather Modeling Framework, which is a 3-D global multi-fluid MHD model of the outer heliosphere with one ion fluid and four neutral populations, for time-dependent 2-D multi-fluid MHD simulations of solar wind propagation from a heliocentric distance of 1 AU up to 50 AU. We used this model to predict the solar wind plasma parameters as well as the interplanetary magnetic field components at Pluto and along the New Horizons trajectory during the whole calendar year of 2015 including the closest approach on July 14. The simulation is run in the solar equatorial plane in the heliographic inertial frame (HGI). The inner boundary conditions along a circle of 1 AU radius are set by near-Earth solar wind observations (hourly OMNI data), assuming that the global solar wind distribution does not change much during a Carrington rotation (27.2753 days). Our 2-D multi-fluid MHD code evolves one ion fluid and two neutral fluids, which are the primary interstellar neutral atoms and the interstellar neutral atoms deflected in the outer heliosheath between the slow bow shock and the heliopause. Spherical expansion effects are properly taken into account for the ions and the solar magnetic field. The inflow parameters of the two neutral fluids (density, temperature, and velocity components) are set at the negative X (HGI) boundary at 50 AU distance, which are taken from previous 3-D global multi-fluid MHD simulations of the heliospheric interface in a much larger simulation box (1500x1500x1500 AU). The inflow velocity vectors of the two neutral fluids define the so-called hydrogen deflection plane. The solar wind ions and the interstellar neutrals interact through charge exchange source terms included in the multi-fluid MHD equations, so the two neutral populations are evolved self-consistently. We validate our model with the available plasma data from New Horizons as well as with Voyager 2 plasma and magnetic field observations within the heliocentric distance of 50 AU. Our new time-dependent 2-D multi-fluid MHD model is generally applicable for solar wind predictions at any outer planet (Jupiter, Saturn, Uranus, Neptune) or spacecraft in the outer heliosphere where charge exchange between solar wind ions and interstellar neutrals play an important role.

Quantum dynamics of charge state in silicon field evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silaeva, Elena P.; Uchida, Kazuki; Watanabe, Kazuyuki, E-mail: kazuyuki@rs.kagu.tus.ac.jp

2016-08-15

The charge state of an ion field-evaporating from a silicon-atom cluster is analyzed using time-dependent density functional theory coupled to molecular dynamics. The final charge state of the ion is shown to increase gradually with increasing external electrostatic field in agreement with the average charge state of silicon ions detected experimentally. When field evaporation is triggered by laser-induced electronic excitations the charge state also increases with increasing intensity of the laser pulse. At the evaporation threshold, the charge state of the evaporating ion does not depend on the electrostatic field due to the strong contribution of laser excitations to themore » ionization process both at low and high laser energies. A neutral silicon atom escaping the cluster due to its high initial kinetic energy is shown to be eventually ionized by external electrostatic field.« less

Configuration interaction in charge exchange spectra of tin and xenon

NASA Astrophysics Data System (ADS)

D'Arcy, R.; Morris, O.; Ohashi, H.; Suda, S.; Tanuma, H.; Fujioka, S.; Nishimura, H.; Nishihara, K.; Suzuki, C.; Kato, T.; Koike, F.; O'Sullivan, G.

2011-06-01

Charge-state-specific extreme ultraviolet spectra from both tin ions and xenon ions have been recorded at Tokyo Metropolitan University. The electron cyclotron resonance source spectra were produced from charge exchange collisions between the ions and rare gas target atoms. To identify unknown spectral lines of tin and xenon, atomic structure calculations were performed for Sn14+-Sn17+ and Xe16+-Xe20+ using the Hartree-Fock configuration interaction code of Cowan (1981 The Theory of Atomic Structure and Spectra (Berkeley, CA: University of California Press)). The energies of the capture states involved in the single-electron process that occurs in these slow collisions were estimated using the classical over-barrier model.

A compact source for bunches of singly charged atomic ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murböck, T.; Birkl, G.; Schmidt, S.

2016-04-15

We have built, operated, and characterized a compact ion source for low-energy bunches of singly charged atomic ions in a vacuum beam line. It is based on atomic evaporation from an electrically heated oven and ionization by electron impact from a heated filament inside a grid-based ionization volume. An adjacent electrode arrangement is used for ion extraction and focusing by applying positive high-voltage pulses to the grid. The method is particularly suited for experimental environments which require low electromagnetic noise. It has proven simple yet reliable and has been used to produce μs-bunches of up to 10{sup 6} Mg{sup +}more » ions at a repetition rate of 1 Hz. We present the concept, setup and characterizing measurements. The instrument has been operated in the framework of the SpecTrap experiment at the HITRAP facility at GSI/FAIR to provide Mg{sup +} ions for sympathetic cooling of highly charged ions by laser-cooled {sup 24}Mg{sup +}.« less

Charge-state distribution of Li ions from the β decay of laser-trapped 6He atoms

NASA Astrophysics Data System (ADS)

Hong, R.; Leredde, A.; Bagdasarova, Y.; Fléchard, X.; García, A.; Knecht, A.; Müller, P.; Naviliat-Cuncic, O.; Pedersen, J.; Smith, E.; Sternberg, M.; Storm, D. Â. W.; Swanson, H. Â. E.; Wauters, F.; Zumwalt, D.

2017-11-01

The accurate determination of atomic final states following nuclear β decay plays an important role in several experiments. In particular, the charge state distributions of ions following nuclear β decay are important for determinations of the β -ν angular correlation with improved precision. Beyond the hydrogenic cases, the decay of neutral 6He presents the simplest case. Our measurement aims at providing benchmarks to test theoretical calculations. The kinematics of Lin + ions produced following the β decay of 6He within an electric field were measured using 6He atoms in the metastable (1 s 2 s ,S31) and (1 s 2 p ,P32) states confined by a magneto-optical trap. The electron shakeoff probabilities were deduced, including their dependence on ion energy. We find significant discrepancies on the fractions of Li ions in the different charge states with respect to a recent calculation.

Impact of local electrostatic field rearrangement on field ionization

NASA Astrophysics Data System (ADS)

Katnagallu, Shyam; Dagan, Michal; Parviainen, Stefan; Nematollahi, Ali; Grabowski, Blazej; Bagot, Paul A. J.; Rolland, Nicolas; Neugebauer, Jörg; Raabe, Dierk; Vurpillot, François; Moody, Michael P.; Gault, Baptiste

2018-03-01

Field ion microscopy allows for direct imaging of surfaces with true atomic resolution. The high charge density distribution on the surface generates an intense electric field that can induce ionization of gas atoms. We investigate the dynamic nature of the charge and the consequent electrostatic field redistribution following the departure of atoms initially constituting the surface in the form of an ion, a process known as field evaporation. We report on a new algorithm for image processing and tracking of individual atoms on the specimen surface enabling quantitative assessment of shifts in the imaged atomic positions. By combining experimental investigations with molecular dynamics simulations, which include the full electric charge, we confirm that change is directly associated with the rearrangement of the electrostatic field that modifies the imaging gas ionization zone. We derive important considerations for future developments of data reconstruction in 3D field ion microscopy, in particular for precise quantification of lattice strains and characterization of crystalline defects at the atomic scale.

Efficient acceleration of neutral atoms in laser produced plasma

DOE PAGES

Dalui, M.; Trivikram, T. M.; Colgan, James Patrick; ...

2017-06-20

Recent advances in high-intensity laser-produced plasmas have demonstrated their potential as compact charge particle accelerators. Unlike conventional accelerators, transient quasi-static charge separation acceleration fields in laser produced plasmas are highly localized and orders of magnitude larger. Manipulating these ion accelerators, to convert the fast ions to neutral atoms with little change in momentum, transform these to a bright source of MeV atoms. The emittance of the neutral atom beam would be similar to that expected for an ion beam. Since intense laser-produced plasmas have been demonstrated to produce high-brightness-low-emittance beams, it is possible to envisage generation of high-flux, low-emittance, highmore » energy neutral atom beams in length scales of less than a millimeter. Here, we show a scheme where more than 80% of the fast ions are reduced to energetic neutral atoms and demonstrate the feasibility of a high energy neutral atom accelerator that could significantly impact applications in neutral atom lithography and diagnostics.« less

Surface and structure modification induced by high energy and highly charged uranium ion irradiation in monocrystal spinel

NASA Astrophysics Data System (ADS)

Yang, Yitao; Zhang, Chonghong; Song, Yin; Gou, Jie; Zhang, Liqing; Meng, Yancheng; Zhang, Hengqing; Ma, Yizhun

2014-05-01

Due to its high temperature properties and relatively good behavior under irradiation, magnesium aluminate spinel (MgAl2O4) is considered as a possible material to be used as inert matrix for the minor actinides burning. In this case, irradiation damage is an unavoidable problem. In this study, high energy and highly charged uranium ions (290 MeV U32+) were used to irradiate monocrystal spinel to the fluence of 1.0 × 1013 ions/cm2 to study the modification of surface and structure. Highly charged ions carry large potential energy, when they interact with a surface, the release of potential energy results in the modification of surface. Atomic force microscopy (AFM) results showed the occurrence of etching on surface after uranium ion irradiation. The etching depth reached 540 nm. The surprising efficiency of etching is considered to be induced by the deposition of potential energy with high density. The X-ray diffraction results showed that the (4 4 0) diffraction peak obviously broadened after irradiation, which indicated that the distortion of lattice has occurred. After multi-peak Gaussian fitting, four Gaussian peaks were separated, which implied that a structure with different damage layers could be formed after irradiation.

Positive and negative contribution to birefringence in a family of carbonates: A Born effective charges analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, Qun; Yang, Guang; Hou, Juan

It is an important topic to investigate the birefringence and reveal the contribution from ions to birefringence because it plays an important role in nonlinear optical materials. In this paper, the birefringence of carbonates with coplanar CO{sub 3} groups were investigated using the first-principles method. The results show that the lead carbonates exhibit relative large birefringence. After detailed investigate the electronic structures, and Born effective charges, the authors find out that anisotropic electron distribution in the CO{sub 3} groups and Pb atoms give positive contribution, while the negative contribution was found from fluorine atoms, meanwhile the Ca, Mg, and Cdmore » atoms give very small contribution to birefringence. - Graphical abstract: Using the DFT and Born effective charges, the birefringence and the contribution of ions were investigated, the positive and negative contribution was found from Pb and F ions, respectively. - Highlights: • Optical properties and Born effective charges of carbonates are investigated. • Lead carbonates exhibit relative large birefringence. • Coplanar CO{sub 3} groups and Pb atoms give positive contribution. • F atoms give negative contribution. • Ca, Mg, and Cd atoms give very small contribution.« less

Charge exchange cross sections in slow collisions of Si3+ with Hydrogen atom

NASA Astrophysics Data System (ADS)

Joseph, Dwayne; Quashie, Edwin; Saha, Bidhan

2011-05-01

In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. Work supported by NSF CREST project (grant #0630370).

EBIT - Electronic Beam Ion Trap: N Divison experimental physics annual report 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, D.

1996-10-01

The multi-faceted research effort of the EBIT (Electron Beam Ion Trap) program in N-Division of the Physics and Space Technology Department at Lawrence Livermore National Laboratory (LLNL) continues to contribute significant results to the physical sciences from studies with low energy very highly charged heavy ions. The EBIT program attracts a number of collaborators from the US and abroad for the different projects. The collaborations are partly carried out through participating graduate students demonstrating the excellent educational capabilities at the LLNL EBIT facilities. Moreover, participants from Historically Black Colleges and Universities are engaged in the EBIT project. This report describesmore » EBIT work for 1995 in atomic structure measurements and radiative transition probabilities, spectral diagnostics for laboratory and astrophysical plasmas, ion/surface interaction studies, electron-ion interactions studies, retrap and ion collisions, and instrumental development.« less

Theory of the stopping power of fast multicharged ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yudin, G.L.

1991-12-01

The processes of Coulomb excitation and ionization of atoms by a fast charged particle moving along a classical trajectory are studied. The target electrons are described by the Dirac equation, while the field of the incident particle is described by the Lienard-Wiechert potential. The theory is formulated in the form most convenient for investigation of various characteristics of semiclassical atomic collisions. The theory of sudden perturbations, which is valid at high enough velocities for a high projectile charge, is employed to obtain probabilities and cross sections of the Coulomb excitation and ionization of atomic hydrogen by fast multiply charged ions.more » Based on the semiclassical sudden Born approximation, the ionization cross section and the average electronic energy loss of a fast ion in a single collision with an atom are investigated over a wide specific energy range from 500 keV/amu to 50 MeV/amu.« less

Total Born approximation cross sections for single electron loss by atoms and ions colliding with atoms

NASA Technical Reports Server (NTRS)

Rule, D. W.

1977-01-01

The first born approximation (FBA) is applied to the calculation of single electron loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions were used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors were used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge was explored in the case of hydrogen-like ions. Scaling of the cross section with respect to the target nuclear charge for electron loss by Fe (+25) in collision with neutral atoms ranging from H to Fe is also examined. These results were compared to those of the binary encounter approximation and to the FBA for the case of ionization by completely stripped target ions.

Scattered Ion Energetics for H atoms Impinging a Copper Surface

NASA Astrophysics Data System (ADS)

Defazio, J. N.; Stephen, T. M.; Peko, B. L.

2002-05-01

The energy loss and charge state of atomic hydrogen scattered from surfaces is important in a broad range of scientific endeavors. These include the charging of spacecraft, the detection of low energy neutrals in the space environment, energy transfer from magnetically confined plasmas and the modeling of low energy electric discharges. Measurements of scattered ions resulting from low energy (20 - 1000 eV) atomic hydrogen impacting a copper surface have been accomplished. Differential energy distributions and yields for H- and H+ resulting from these collisions are presented. The data show that the energy distributions develop a universal dependence, when scaled by the incident energy. These results are compared with studies involving incident hydrogen ions. For incident energies less than 100eV, there are obvious differences in the scattered ion energy distributions resulting from impacting atoms when compared to those resulting from ions.

Relationship between ion pair geometries and electrostatic strengths in proteins.

PubMed Central

Kumar, Sandeep; Nussinov, Ruth

2002-01-01

The electrostatic free energy contribution of an ion pair in a protein depends on two factors, geometrical orientation of the side-chain charged groups with respect to each other and the structural context of the ion pair in the protein. Conformers in NMR ensembles enable studies of the relationship between geometry and electrostatic strengths of ion pairs, because the protein structural contexts are highly similar across different conformers. We have studied this relationship using a dataset of 22 unique ion pairs in 14 NMR conformer ensembles for 11 nonhomologous proteins. In different NMR conformers, the ion pairs are classified as salt bridges, nitrogen-oxygen (N-O) bridges and longer-range ion pairs on the basis of geometrical criteria. In salt bridges, centroids of the side-chain charged groups and at least a pair of side-chain nitrogen and oxygen atoms of the ion-pairing residues are within a 4 A distance. In N-O bridges, at least a pair of the side-chain nitrogen and oxygen atoms of the ion-pairing residues are within 4 A distance, but the distance between the side-chain charged group centroids is greater than 4 A. In the longer-range ion pairs, the side-chain charged group centroids as well as the side-chain nitrogen and oxygen atoms are more than 4 A apart. Continuum electrostatic calculations indicate that most of the ion pairs have stabilizing electrostatic contributions when their side-chain charged group centroids are within 5 A distance. Hence, most (approximately 92%) of the salt bridges and a majority (68%) of the N-O bridges are stabilizing. Most (approximately 89%) of the destabilizing ion pairs are the longer-range ion pairs. In the NMR conformer ensembles, the electrostatic interaction between side-chain charged groups of the ion-pairing residues is the strongest for salt bridges, considerably weaker for N-O bridges, and the weakest for longer-range ion pairs. These results suggest empirical rules for stabilizing electrostatic interactions in proteins. PMID:12202384

Charge-state distribution of Li ions from the β decay of laser-trapped He 6 atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, R.; Leredde, A.; Bagdasarova, Y.

The accurate determination of atomic final states following nuclear β decay plays an important role in several experiments. In particular, the charge state distributions of ions following nuclear β decay are important for determinations of the β-ν angular correlation with improved precision. Also, beyond the hydrogenic cases, the decay of neutral 6He presents the simplest case. Our measurement aims at providing benchmarks to test theoretical calculations. The kinematics of Li n+ ions produced following the β decay of 6He within an electric field were measured using 6He atoms in the metastable (1s2s, 3S 1) and (1s2p, 3P 2) states confinedmore » by a magneto-optical trap. The electron shakeoff probabilities were deduced, including their dependence on ion energy. Finally, we find significant discrepancies on the fractions of Li ions in the different charge states with respect to a recent calculation.« less

Charge-state distribution of Li ions from the β decay of laser-trapped He 6 atoms

DOE PAGES

Hong, R.; Leredde, A.; Bagdasarova, Y.; ...

2017-11-13

The accurate determination of atomic final states following nuclear β decay plays an important role in several experiments. In particular, the charge state distributions of ions following nuclear β decay are important for determinations of the β-ν angular correlation with improved precision. Also, beyond the hydrogenic cases, the decay of neutral 6He presents the simplest case. Our measurement aims at providing benchmarks to test theoretical calculations. The kinematics of Li n+ ions produced following the β decay of 6He within an electric field were measured using 6He atoms in the metastable (1s2s, 3S 1) and (1s2p, 3P 2) states confinedmore » by a magneto-optical trap. The electron shakeoff probabilities were deduced, including their dependence on ion energy. Finally, we find significant discrepancies on the fractions of Li ions in the different charge states with respect to a recent calculation.« less

METHOD AND APPARATUS FOR TRAPPING IONS IN A MAGNETIC FIELD

DOEpatents

Luce, J.S.

1962-04-17

A method and apparatus are described for trapping ions within an evacuated container and within a magnetic field utilizing dissociation and/or ionization of molecular ions to form atomic ions and energetic neutral particles. The atomic ions are magnetically trapped as a result of a change of charge-to- mass ratio. The molecular ions are injected into the container and into the path of an energetic carbon arc discharge which dissociates and/or ionizes a portion of the molecular ions into atomic ions and energetic neutrals. The resulting atomic ions are trapped by the magnetic field to form a circulating beam of atomic ions, and the energetic neutrals pass out of the system and may be utilized in a particle accelerator. (AEC)

Symmetric Resonance Charge Exchange Cross Section Based on Impact Parameter Treatment

NASA Technical Reports Server (NTRS)

Omidvar, Kazem; Murphy, Kendrah; Atlas, Robert (Technical Monitor)

2002-01-01

Using a two-state impact parameter approximation, a calculation has been carried out to obtain symmetric resonance charge transfer cross sections between nine ions and their parent atoms or molecules. Calculation is based on a two-dimensional numerical integration. The method is mostly suited for hydrogenic and some closed shell atoms. Good agreement has been obtained with the results of laboratory measurements for the ion-atom pairs H+-H, He+-He, and Ar+-Ar. Several approximations in a similar published calculation have been eliminated.

Charge and Exchange

NASA Technical Reports Server (NTRS)

2008-01-01

Even though comets are basically giant dirty snowballs, a few years ago they surprised astronomers by emitting X-radiation. These X-rays are not produced by multi-million degree gas (as is often the case) but rather by a process called 'charge exchange'. In this process, ionized atoms (which have lost one or more electrons) which are carried within the solar wind collide with neutral atoms in the comet's coma. The solar wind ion can collide with and capture an electron from the neutral comet atom, and in doing so some of the energy of the collision is observed in the form of X-rays. This produces a glow of X-rays on the sunward side of the comet's atmosphere. Charge exchange can occur in a variety of astrophysical settings, and cometary charge exchange provides astronomers a means to study this process up close. The image above is a pretty picture of comet 73P/Schwassmann-Wachmann 3 passing by the Ring Nebula. This image was obtained by the ultraviolet and optical telescope (UVOT) on the Swift gamma-ray burst hunter. The UVOT observations help astronomers to study the structure and chemistry of the comet, while Swift's X-ray Telescope (XRT) simultaneously monitors the charge exchange process. Comet 73P/Schwassmann-Wachmann 3 is currently in the process of breaking up, and the UVOT observations show important details of how this breakup is occurring.

Interatomic Coulombic Decay: The Mechanism for Rapid Deexcitation of Hollow Atoms.

PubMed

Wilhelm, Richard A; Gruber, Elisabeth; Schwestka, Janine; Kozubek, Roland; Madeira, Teresa I; Marques, José P; Kobus, Jacek; Krasheninnikov, Arkady V; Schleberger, Marika; Aumayr, Friedrich

2017-09-08

The impact of a highly charged ion onto a solid gives rise to charge exchange between the ion and target atoms, so that a slow ion gets neutralized in the vicinity of the surface. Using highly charged Ar and Xe ions and the surface-only material graphene as a target, we show that the neutralization and deexcitation of the ions proceeds on a sub-10 fs time scale. We further demonstrate that a multiple Interatomic Coulombic Decay (ICD) model can describe the observed ultrafast deexcitation. Other deexcitation mechanisms involving nonradiative decay and quasimolecular orbital formation during the impact are not important, as follows from the comparison of our experimental data with the results of first-principles calculations. Our method also enables the estimation of ICD rates directly.

Reactions between NO/+/ and metal atoms using magnetically confined afterglows

NASA Technical Reports Server (NTRS)

Lo, H. H.; Clendenning, L. M.; Fite, W. L.

1977-01-01

A new method of studying thermal energy ion-neutral collision processes involving nongaseous neutral atoms is described. A long magnetic field produced by a solenoid in a vacuum chamber confines a thermal-energy plasma generated by photoionization of gas at very low pressure. As the plasma moves toward the end of the field, it is crossed by a metal atom beam. Ionic products of ion-atom reactions are trapped by the field and both the reactant and product ions move to the end of the magnetic field where they are detected by a quadrupole mass filter. The cross sections for charge transfer between NO(+) and Na, Mg, Ca, and Sr and that for rearrangement between NO(+) and Ca have been obtained. The charge-transfer reaction is found strongly dominant over the rearrangement reaction that forms metallic oxide ions.

Spontaneous Mass and Charge Losses from Single Multi-Megadalton Ions Studied by Charge Detection Mass Spectrometry

NASA Astrophysics Data System (ADS)

Keifer, David Z.; Alexander, Andrew W.; Jarrold, Martin F.

2017-03-01

Spontaneous mass and charge losses from individual multi-megadalton ions have been observed with charge detection mass spectrometry (CDMS) by trapping single hepatitis B virus (HBV) capsids for 3 s. Gradual increases in the oscillation frequency of single ions in the ion trap are attributed mainly to mass loss (probably solvent, water, and/or salt). The total mass lost during the 3 s trapping period peaks at around 20 kDa for 4 MDa HBV T = 4 capsids. Discrete frequency drops punctuate the gradual increases in the oscillation frequencies. The drops are attributed to a sudden loss of charge. In most cases a single positive charge is lost along with some mass (on average around 1000 Da). Charge loss occurs for over 40% of the trapped ions. It usually occurs near the beginning of the trapping event, and it occurs preferentially in regions of the trap with strong electric fields, indicating that external electric fields promote charge loss. This process may contribute to the decrease in m/ z resolution that often occurs with megadalton ions.

Differential multi-electron emission induced by swift highly charged gold ions penetrating carbon foils

NASA Astrophysics Data System (ADS)

Rothard, H.; Moshammer, R.; Ullrich, J.; Kollmus, H.; Mann, R.; Hagmann, S.; Zouros, T. J. M.

2007-05-01

First results on swift heavy ion induced electron emission from solids obtained with a reaction microscope are presented. This advanced technique, which is successfully used since quite some time to study electron ejection in ion-atom collisions, combines the measurement of the time-of-flight of electrons with imaging techniques. A combination of electric and magnetic fields guides the ejected electrons onto a position sensitive detector, which is capable to accept multiple hits. From position and time-of-flight measurement the full differential emission characteristics of up to 10 electrons per single incoming ion can be extracted. As a first example, we show energy spectra, angular distributions and the multiplicity distribution of electrons from impact of Au24+ (11 MeV/u) on a thin carbon foil (28 μg/cm2).

Hydrogen rearrangements in the fragmentation of anthracene by low-energy electron impact

NASA Astrophysics Data System (ADS)

van der Burgt, Peter J. M.; Dunne, Melissa; Gradziel, Marcin L.

2018-02-01

We have measured mass spectra for positive ions produced by low-energy electron impact on anthracene using a reflectron time-of-flight mass spectrometer. The electron impact energy has been varied from 0 to 100 eV in steps of 0.5 eV. Ion yield curves of most of the fragment ions have been determined by fitting groups of adjacent peaks in the mass spectra with sequences of normalized Gaussians. Appearance energies for all these ions have been determined, and we report the first direct measurement of the triple ionization energy of anthracene at 45.5±0.5 eV. The groups of fragments containing 8-13 carbon atoms provide evidence for hydrogen rearrangements during the fragmentation, involving retention or loss of one or two additional hydrogen atoms. Groups of fragments with 6 and 7 carbon atoms clearly show the presence of doubly-charged fragments. The smaller fragments with 1-4 carbon atoms all show broadened peaks, and these fragments may be partly or mostly due to energetic charge-separation fragmentations of doubly-charged anthracene.

Collaborative Research: A Model of Partially Ionized Plasma Flows with Kinetic Treatment of Neutral Atoms and Nonthermal Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogorelov, Nikolai; Zhang, Ming; Borovikov, Sergey

Interactions of flows of partially ionized, magnetized plasma are frequently accompanied by the presence of both thermal and non-thermal (pickup) ion components. Such interactions cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a nonthermal component of ions is formed due to charge exchange and collisions between the thermal (core) ions and neutrals, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, e. g., takes place in the outer heliosphere - the part ofmore » interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. This is also possible in laboratory, at million degrees and above, when plasma is conducting electricity far too well, which makes Ohmic heating ineffective. To attain the target temperatures one needs additional heating eventually playing a dominant role. Among such sources is a so-called neutral particle beam heating. This is a wide-spread technique (Joint European Torus and International Thermonuclear Experimental Reactor experiments) based on the injection of powerful beams of neutral atoms into ohmically preheated plasma. In this project we have investigated the energy and density separation between the thermal and nonthermal components in the solar wind and interstellar plasmas. A new model has been developed in which we solve the ideal MHD equations for mixture of all ions and the kinetic Boltzmann equation to describe the transport of neutral atoms. As a separate capability, we can treat the flow of neutral atoms in a multi-component fashion, where neutral atoms born in each thermodynamically distinct regions are governed by the Euler gas dynamic equations. We also describe the behavior of pickup ions either kinetically, using the Fokker–Planck equation, or as a separate fluid. Our numerical simulations have demonstrated that pickup ions play a major role in the interaction of the solar wind and (partially ionized) interstellar medium plasmas. Our teams have investigated the stability of the surface (the heliopause) that separates the solar wind from the local interstellar medium, the transport of galactic cosmic rays, the properties of the heliotail flow, and modifications to the bow wave in front of the heliopause due to charge exchange between the neutral H atoms born in the solar wind and interstellar ions. Modeling results have been validated against observational data, such as obtained by the Interstellar Boundary Explorer (IBEX), and made it possible to shed light on the structure of energetic neutral atom maps created by this spacecraft.. We have also demonstrated that charge-exchange modulated heliosphere is a source of anisotropy of the multi-TeV cosmic ray flux observed in a number of Earth-bound air shower experiments. Newly developed codes are implemented within a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), a publicly available code being developed by our team for over 12 years. MS-FLUKSS scales well up to 160,000 computing cores and has been ported on major supercomputers in the country. Efficient parallelization and data choreography in the continuum simulation modules are provided by Chombo, an adaptive mesh refinement framework managed by Phillip Colella’s team at LBNL. We have implemented in-house, hybrid (MPI+OpenMP) parallelization of the kinetic modules that solve the Boltzmann equation with a Monte Carlo method. Currently, the kinetic modules are being rewritten to take advantage of the modern CPU-GPU supercomputer architecture. The scope of the project allowed us to enhance plasma research and education in such broad, multidis- ciplinary field as physics of partially ionized plasma and its application to space physics and fusion science. Besides the impact on the modeling of complex physical systems, our approach to computational resource management for complex codes utilizing multiple algorithm technologies appears to be a major advance on current approaches. The development of sophisticated resource management will be essential for all future modeling efforts that incorporate a diversity of scales and physical processes. Our effort provided leadership in promoting computational science and plasma physics within the UAH and FIT campuses and, through the training of a broad spectrum of scientists and engineers, foster new technologies across the country.« less

Collaborative Research: A Model of Partially Ionized Plasma Flows with Kinetic Treatment of Neutral Atoms and Nonthermal Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogorelov, Nikolai; Zhang, Ming

Interactions of flows of partially ionized, magnetized plasma are frequently accompanied by the presence of both thermal and non-thermal (pickup) ion components. Such interactions cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a nonthermal component of ions is formed due to charge exchange and collisions between the thermal (core) ions and neutrals, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, e. g., takes place in the outer heliosphere –- the part ofmore » interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. This is also possible in laboratory, at million degrees and above, when plasma is conducting electricity far too well, which makes Ohmic heating ineffective. To attain the target temperatures one needs additional heating eventually playing a dominant role. Among such sources is a so-called neutral particle beam heating. This is a wide-spread technique (Joint European Torus and International Thermonuclear Experimental Reactor experiments) based on the injection of powerful beams of neutral atoms into ohmically preheated plasma. In this project we have investigated the energy and density separation between the thermal and nonthermal components in the solar wind and interstellar plasmas. A new model has been developed in which we solve the ideal MHD equations for mixture of all ions and the kinetic Boltzmann equation to describe the transport of neutral atoms. As a separate capability, we can treat the flow of neutral atoms in a multi-component fashion, where neutral atoms born in each thermodynamically distinct region are governed by the Euler gas dynamic equations. We also describe the behavior of pickup ions either kinetically, using the Fokker--Planck equation, or as a separate fluid. Our numerical simulations have demonstrated that pickup ions play a major role in the interaction of the solar wind and (partially ionized) interstellar medium plasmas. Our teams have investigated the stability of the surface (the heliopause) that separates the solar wind from the local interstellar medium, the transport of galactic cosmic rays, the properties of the heliotail flow, and modifications to the bow wave in front of the heliopause due to charge exchange between the neutral H atoms born in the solar wind and interstellar ions. Modeling results have been validated against observational data, such as obtained by the Interstellar Boundary Explorer (IBEX), and made it possible to shed light on the structure of energetic neutral atom maps created by this spacecraft.. We have also demonstrated that charge-exchange modulated heliosphere is a source of anisotropy of the multi-TeV cosmic ray flux observed in a number of Earth-bound air shower experiments. Newly developed codes are implemented within a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), a publicly available code being developed by our team for over 12 years. MS-FLUKSS scales well up to 160,000 computing cores and has been ported on major supercomputers in the country. Efficient parallelization and data choreography in the continuum simulation modules are provided by Chombo, an adaptive mesh refinement framework managed by Phillip Colella's team at LBNL. We have implemented in-house, hybrid (MPI+OpenMP) parallelization of the kinetic modules that solve the Boltzmann equation with a Monte Carlo method. Currently, the kinetic modules are being rewritten to take advantage of the modern CPU-GPU supercomputer architecture. The scope of the project allowed us to enhance plasma research and education in such broad, multidisciplinary field as physics of partially ionized plasma and its application to space physics and fusion science. Besides the impact on the modeling of complex physical systems, our approach to computational resource management for complex codes utilizing multiple algorithm technologies appears to be a major advance on current approaches. The development of sophisticated resource management will be essential for all future modeling efforts that incorporate a diversity of scales and physical processes. Our effort provided leadership in promoting computational science and plasma physics within the UAH and FIT campuses and, through the training of a broad spectrum of scientists and engineers, fostering new technologies across the country.« less

Status of Charge Exchange Cross Section Measurements for Highly Charged Ions on Atomic Hydrogen

NASA Astrophysics Data System (ADS)

Draganic, I. N.; Havener, C. C.; Schultz, D. R.; Seely, D. G.; Schultz, P. C.

2011-05-01

Total cross sections of charge exchange (CX) for C5+, N6+, and O7+ ions on ground state atomic hydrogen are measured in an extended collision energy range of 1 - 20,000 eV/u. Absolute CX measurements are performed using an improved merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source mounted on a high voltage platform. In order to improve the problematic H+ signal collection for these exoergic CX collisions at low relative energies, a new double focusing electrostatic analyzer was installed. Experimental CX data are in good agreement with all previous H-oven relative measurements at higher collision energies. We compare our results with the most recent molecular orbital close-coupling (MOCC) and atomic orbital close-coupling (AOCC) theoretical calculations. Work supported by the NASA Solar & Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences, and the Office of Basic Energy Sciences of the U.S. DoE.

Ionization source utilizing a multi-capillary inlet and method of operation

DOEpatents

Smith, Richard D.; Kim, Taeman; Udseth, Harold R.

2004-10-12

A multi-capillary inlet to focus ions and other charged particles generated at or near atmospheric pressure into a relatively low pressure region, which allows increased conductance of ions and other charged particles. The multi-capillary inlet is juxtaposed between an ion source and the interior of an instrument maintained at near atmospheric pressure, it finds particular advantages when deployed to improve the ion transmission between an electrospray ionization source and the first vacuum stage of a mass spectrometer, and finds its greatest advantages when deployed in conjunction with an electrodynamic (RF) ion funnel deployed within the interior of the mass spectrometer, particularly an ion funnel equipped with a jet disturber.

Analytic treatment of charge cloud overlaps: an improvement of the tomographic atom probe efficiency

NASA Astrophysics Data System (ADS)

Bas, P.; Bostel, A.; Grancher, G.; Deconihout, B.; Blavette, D.

1996-03-01

Although reliable position and composition data are obtained with the Tomographic Atom Probe, the procedure of position calculation by charge centroiding fails when the detector receives two or more ions with close spaced positions and the same mass-to-charge ratio. As the charge clouds of the ions overlap, they form a unique charge pattern on the multianode detector. Only one atom is represented and its position is biased. In order to estimate real positions, we have developed a correction method. The spatial distribution of charges inside a cloud issued from one impact is modelled by a Gaussian law. The particular properties of the Gaussian enable the calculation of exact positions of the two impacts of the overlapped charge patterns and charges of corresponding clouds. The calculation may be generalized for more than two overlapped clouds. The method was tested on a plane-by-plane analysis of a fully ordered Cu 3Au alloy performed on a (100) pole.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meusel, O., E-mail: o.meusel@iap.uni-frankfurt.de; Droba, M.; Noll, D.

The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree ofmore » space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed.« less

Signatures of the atomic nucleus in laser-assisted single ionization of one-electron atoms

NASA Astrophysics Data System (ADS)

Ajana, Imane; Khalil, Driss; Makhoute, Abdelkader

2018-03-01

The dynamics of the electron-impact single ionization of hydrogenic targets in the presence of a laser field (e, 2e) has been studied for different residual ion charges Z = 1, 2, 3 and 4. The state of fast electron in the laser field is described by the Volkov state, while the dressed state of the ejected slow electron and atomic target is treated perturbatively to the first-order perturbation theory. We calculate the triple differential cross section in the Ehrhardt asymmetric coplanar geometry. We have compared and analyzed the triple differential cross sections from one-electron atoms by varying the charge state of the residual ion, and evaluating the interplay between the laser influence and the role of scattering from the residual ion.

Thermal-energy reactions of O2(2+) ions with O2, N2, CO2, NO, and Ne

NASA Technical Reports Server (NTRS)

Chatterjee, B. K.; Johnson, R.

1989-01-01

The paper presents results of drift-tube mass-spectrometer studies of the reactivity of doubly charged molecular oxygen ions with several molecules and neon atoms. Thermal-energ rate coefficients for the reactions with the molecular reactants were found to be large, close to the limiting Langevin rates. Charge transfer with neon atoms was observed, but the measured rate coefficient was only a small fraction of the Langevin rate. It is concluded that the measured rate constants for the reactions considereed refer to vibrationally excited ions.

Charge transfer collisions of Si^3+ with H at low energies

NASA Astrophysics Data System (ADS)

Joseph, D. C.; Gu, J. P.; Saha, B. C.

2009-11-01

Charge transfer of positively charged ions with atomic hydrogen is important not only in magnetically confined plasmas between impurity ions and H atoms from the chamber walls influences the overall ionization balance and effects the plasma cooling but also in astrophysics, where it plays a key role in determining the properties of the observed gas. It also provides a recombination mechanism for multiply charged ions in X-ray ionized astronomical environments. We report an investigation using the molecular-orbital close-coupling (MOCC) method, both quantum mechanically and semi-classically, in the adiabatic representation. Ab initio adiabatic potentials and coupling matrix elements--radial and angular--are calculated using the MRD-CI method. Comparison of our results with other theoretical as well as experimental findings will be discussed.

Focal-surface detector for heavy ions

DOEpatents

Erskine, John R.; Braid, Thomas H.; Stoltzfus, Joseph C.

1979-01-01

A detector of the properties of individual charged particles in a beam includes a gridded ionization chamber, a cathode, a plurality of resistive-wire proportional counters, a plurality of anode sections, and means for controlling the composition and pressure of gas in the chamber. Signals generated in response to the passage of charged particles can be processed to identify the energy of the particles, their loss of energy per unit distance in an absorber, and their angle of incidence. In conjunction with a magnetic spectrograph, the signals can be used to identify particles and their state of charge. The detector is especially useful for analyzing beams of heavy ions, defined as ions of atomic mass greater than 10 atomic mass units.

Effects of Ion Atomic Number on Single-Event Gate Rupture (SEGR) Susceptibility of Power MOSFETs

NASA Technical Reports Server (NTRS)

Lauenstein, J.-M.; Goldsman, N.; Liu, S.; Titus, J.; Ladbury, R. L.; Kim, H. S.; Phan, A. M.; Zafrani, M.; Sherman, P.

2011-01-01

The relative importance of heavy-ion interaction with the oxide, charge ionized in the epilayer, and charge ionized in the drain substrate, on the bias for SEGR failure is experimentally investigated.

Energetic Nitrogen Ions within the Inner Magnetosphere of Saturn

NASA Astrophysics Data System (ADS)

Sittler, E. C.; Johnson, R. E.; Richardson, J. D.; Jurac, S.; Moore, M.; Cooper, J. F.; Mauk, B. H.; Smith, H. T.; Michael, M.; Paranicus, C.; Armstrong, T. P.; Tsurutani, B.; Connerney, J. E. P.

2003-05-01

Titan's interaction with Saturn's magnetosphere will result in the energetic ejection of atomic nitrogen atoms into Saturn's magnetosphere due to dissociation of N2 by electrons, ions, and UV photons. The ejection of N atoms into Saturn's magnetosphere will form a nitrogen torus around Saturn with mean density of about 4 atoms/cm3 with source strength of 4.5x1025 atoms/sec. These nitrogen atoms are ionized by photoionization, electron impact ionization and charge exchange reactions producing an N+ torus of 1-4 keV suprathermal ions centered on Titan's orbital position. We will show Voyager plasma observations that demonstrate presence of a suprathermal ion component within Saturn's outer magnetosphere. The Voyager LECP data also reported the presence of inward diffusing energetic ions from the outer magnetosphere of Saturn, which could have an N+ contribution. If so, when one conserves the first and second adiabatic invariant the N+ ions will have energies in excess of 100 keV at Dione's L shell and greater than 400 keV at Enceladus' L shell. Energetic charged particle radial diffusion coefficients are also used to constrain the model results. But, one must also consider the solar wind as another important source of keV ions, in the form of protons and alpha particles, for Saturn's outer magnetosphere. Initial estimates indicate that a solar wind source could dominate in the outer magnetosphere, but various required parameters for this estimate are highly uncertain and will have to await Cassini results for confirmation. We show that satellite sweeping and charged particle precipitation within the middle and outer magnetosphere will tend to enrich N+ ions relative to protons within Saturn's inner magnetosphere as they diffuse radially inward for radial diffusion coefficients that do not violate observations. Charge exchange reactions within the inner magnetosphere can be an important loss mechanism for O+ ions, but to a lesser degree for N+ ions. Initial LECP results using composition data at energies greater than 200 keV/nucl., showed that heavy ions within Saturn's inner magnetosphere dominated over protons, but that contrary to original suggestions that these ions were O+ , we now argue that they are instead N+ ions. With energetic N+ ions bombarding the icy satellite surfaces chemical reactions can occur at the end of the ion tracks and produce nitrogen oxides or other nitrogen containing molecules such that the radiology within the icy surfaces is driven by the impacting energetic nitrogen ions. These can accumulate over the lifetime of the Saturn system.

Generation and acceleration of neutral atoms in intense laser plasma experiments

NASA Astrophysics Data System (ADS)

Tata, Sheroy; Mondal, Angana; Sarkar, Shobhik; Ved, Yash; Lad, Amit D.; Pasley, John; Colgan, James; Krishnamurthy, M.

2017-10-01

The interaction of a high intensity (>=1018 W/cm2), high contrast (>=109), ultra-short (30fs) laser with solid targets generates a highly dense hot plasma. The quasi-static electric fields in such plasmas are well known for ion acceleration via the target normal sheath acceleration process. Under such conditions charge reduction to generate fast neutral atoms is almost inhibited. Improvised Thomson parabola spectrometry with improved signal to noise ratio has enabled us to measure the signals of fast neutral atoms and negative ions having energies in excess of tens of keV. A study on the neutralization of accelerated protons in plasma shows that the neutral atom to all particle ratio rises sharply from a few percent at the highest detectable energy to 50 % at 15 keV. Using usual charge transfer reactions the generation of neutral atoms can not be explained, thus we conjecture that the neutralization of the accelerated ions is not from the hot dense region of the plasma but neutral atom formation takes place by co-propagating ions with low energy electrons enhancing the effective neutral ratio.

Laboratory Studies of Thermal Energy Charge Transfer of Multiply Charged Ions in Astrophysical Plasmas

NASA Technical Reports Server (NTRS)

Kwong, Victor H. S.

2003-01-01

The laser ablation/ion storage facility at the UNLV Physics Department has been dedicated to the study of atomic and molecular processes in low temperature plasmas. Our program focuses on the charge transfer (electron capture) of multiply charged ions and neutrals important in astrophysics. The electron transfer reactions with atoms and molecules is crucial to the ionization condition of neutral rich photoionized plasmas. With the successful deployment of the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Chandra X-ray Observatory by NASA high resolution VUV and X-ray emission spectra fiom various astrophysical objects have been collected. These spectra will be analyzed to determine the source of the emission and the chemical and physical environment of the source. The proper interpretation of these spectra will require complete knowledge of all the atomic processes in these plasmas. In a neutral rich environment, charge transfer can be the dominant process. The rate coefficients need to be known accurately. We have also extended our charge transfer measurements to KeV region with a pulsed ion beam. The inclusion of this facility into our current program provides flexibility in extending the measurement to higher energies (KeV) if needed. This flexibility enables us to address issues of immediate interest to the astrophysical community as new observations are made by high resolution space based observatories.

Spectroscopic Investigations of Highly Charged Tungsten Ions - Atomic Spectroscopy and Fusion Plasma Diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clementson, Joel

2010-05-01

The spectra of highly charged tungsten ions have been investigated using x-ray and extreme ultraviolet spectroscopy. These heavy ions are of interest in relativistic atomic structure theory, where high-precision wavelength measurements benchmark theoretical approaches, and in magnetic fusion research, where the ions may serve to diagnose high-temperature plasmas. The work details spectroscopic investigations of highly charged tungsten ions measured at the Livermore electron beam ion trap (EBIT) facility. Here, the EBIT-I and SuperEBIT electron beam ion traps have been employed to create, trap, and excite tungsten ions of M- and L-shell charge states. The emitted spectra have been studied inmore » high resolution using crystal, grating, and x-ray calorimeter spectrometers. In particular, wavelengths of n = 0 M-shell transitions in K-like W 55+ through Ne-like W 64+, and intershell transitions in Zn-like W 44+ through Co-like W 47+ have been measured. Special attention is given to the Ni-like W46+ ion, which has two strong electric-dipole forbidden transitions that are of interest for plasma diagnostics. The EBIT measurements are complemented by spectral modeling using the Flexible Atomic Code (FAC), and predictions for tokamak spectra are presented. The L-shell tungsten ions have been studied at electron-beam energies of up to 122 keV and transition energies measured in Ne-like W 64+ through Li-like W 71+. These spectra constitute the physics basis in the design of the ion-temperature crystal spectrometer for the ITER tokamak. Tungsten particles have furthermore been introduced into the Sustained Spheromak Physics Experiment (SSPX) spheromak in Livermore in order to investigate diagnostic possibilities of extreme ultraviolet tungsten spectra for the ITER divertor. The spheromak measurement and spectral modeling using FAC suggest that tungsten ions in charge states around Er-like W 6+ could be useful for plasma diagnostics.« less

Disordering of ultra thin WO3 films by high-energy ions

NASA Astrophysics Data System (ADS)

Matsunami, N.; Kato, M.; Sataka, M.; Okayasu, S.

2017-10-01

We have studied disordering or atomic structure modification of ultra thin WO3 films under impact of high-energy ions with non-equilibrium and equilibrium charge incidence, by means of X-ray diffraction (XRD). WO3 films were prepared by thermal oxidation of W deposited on MgO substrate. Film thickness obtained by Rutherford backscattering spectrometry (RBS) is as low as 2 nm. Smoothness of film surface was observed by atomic force microscopy. It is found that the ratio of XRD intensity degradation per 90 MeV Ni+10 ion (the incident charge is lower than the equilibrium charge) to that per 90 MeV Ni ion with the equilibrium charge depends on the film thickness. Also, film thickness dependence is observed for 100 MeV Xe+14. By comparison of the experimental result with a simple model calculation based on the assumption that the mean charge of ions along the depth follows a saturation curve with power-law approximation to the charge dependent electronic stopping power, the characteristic length attaining the equilibrium charge is obtained to be ∼7 nm for 90 MeV Ni+10 ion incidence or the electron loss cross section of ∼1016 cm2, demonstrating that disordering of ultra WO3 films has been observed and a fundamental quantity can be derived through material modification.

Highly charged ion based time of flight emission microscope

DOEpatents

Barnes, Alan V.; Schenkel, Thomas; Hamza, Alex V.; Schneider, Dieter H.; Doyle, Barney

2001-01-01

A highly charged ion based time-of-flight emission microscope has been designed, which improves the surface sensitivity of static SIMS measurements because of the higher ionization probability of highly charged ions. Slow, highly charged ions are produced in an electron beam ion trap and are directed to the sample surface. The sputtered secondary ions and electrons pass through a specially designed objective lens to a microchannel plate detector. This new instrument permits high surface sensitivity (10.sup.10 atoms/cm.sup.2), high spatial resolution (100 nm), and chemical structural information due to the high molecular ion yields. The high secondary ion yield permits coincidence counting, which can be used to enhance determination of chemical and topological structure and to correlate specific molecular species.

Monte Carlo simulation of neutral-beam injection for mirror fusion reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Ronald Lee

1979-01-01

Computer simulation techniques using the Monte Carlo method have been developed for application to the modeling of neutral-beam intection into mirror-confined plasmas of interest to controlled thermonuclear research. The energetic (10 to 300 keV) neutral-beam particles interact with the target plasma (T i ~ 10 to 100 keV) through electron-atom and ion-atom collisional ionization as well as ion-atom charge-transfer (charge-exchange) collisions to give a fractional trapping of the neutral beam and a loss of charge-transfer-produced neutrals which escape to bombard the reactor first wall. Appropriate interaction cross sections for these processes are calculated for the assumed anisotropic, non-Maxwellian plasma ionmore » phase-space distributions.« less

Probing the Surface Charge on the Basal Planes of Kaolinite Particles with High-Resolution Atomic Force Microscopy

PubMed Central

2017-01-01

High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl2 concentration. Using DLVO theory with charge regulation, we determine from the measured force–distance curves the surface charge distribution on both the silica-like and the gibbsite-like basal plane of the kaolinite particles. We observe that both basal planes do carry charge that varies with pH and salt concentration. The silica facet was found to be negatively charged at pH 4 and above, whereas the gibbsite facet is positively charged at pH below 7 and negatively charged at pH above 7. Investigations in CaCl2 at pH 6 show that the surface charge on the gibbsite facet increases for concentration up to 10 mM CaCl2 and starts to decrease upon further increasing the salt concentration to 50 mM. The increase of surface charge at low concentration is explained by Ca2+ ion adsorption, while Cl– adsorption at higher CaCl2 concentrations partially neutralizes the surface charge. Atomic resolution imaging and density functional theory calculations corroborate these observations. They show that hydrated Ca2+ ions can spontaneously adsorb on the gibbsite facet of the kaolinite particle and form ordered surface structures, while at higher concentrations Cl– ions will co-adsorb, thereby changing the observed ordered surface structure. PMID:29140711

Probing the Surface Charge on the Basal Planes of Kaolinite Particles with High-Resolution Atomic Force Microscopy.

PubMed

Kumar, N; Andersson, M P; van den Ende, D; Mugele, F; Siretanu, I

2017-12-19

High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl 2 concentration. Using DLVO theory with charge regulation, we determine from the measured force-distance curves the surface charge distribution on both the silica-like and the gibbsite-like basal plane of the kaolinite particles. We observe that both basal planes do carry charge that varies with pH and salt concentration. The silica facet was found to be negatively charged at pH 4 and above, whereas the gibbsite facet is positively charged at pH below 7 and negatively charged at pH above 7. Investigations in CaCl 2 at pH 6 show that the surface charge on the gibbsite facet increases for concentration up to 10 mM CaCl 2 and starts to decrease upon further increasing the salt concentration to 50 mM. The increase of surface charge at low concentration is explained by Ca 2+ ion adsorption, while Cl - adsorption at higher CaCl 2 concentrations partially neutralizes the surface charge. Atomic resolution imaging and density functional theory calculations corroborate these observations. They show that hydrated Ca 2+ ions can spontaneously adsorb on the gibbsite facet of the kaolinite particle and form ordered surface structures, while at higher concentrations Cl - ions will co-adsorb, thereby changing the observed ordered surface structure.

Single-atom detection of isotopes

DOEpatents

Meyer, Fred W.

2002-01-01

A method for performing accelerator mass spectrometry, includes producing a beam of positive ions having different multiple charges from a multicharged ion source; selecting positive ions having a charge state of from +2 to +4 to define a portion of the beam of positive ions; and scattering at least a portion of the portion of the beam of positive ions off a surface of a target to directly convert a portion of the positive ions in the portion of the beam of positive ions to negative ions.

Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: I. Thomas related mechanisms

NASA Astrophysics Data System (ADS)

Safarzade, Zohre; Fathi, Reza; Shojaei Akbarabadi, Farideh; Bolorizadeh, Mohammad A.

2018-04-01

The scattering of a completely bare ion by atoms larger than hydrogen is at least a four-body interaction, and the charge transfer channel involves a two-step process. Amongst the two-step interactions of the high-velocity single charge transfer in an anion-atom collision, there is one whose amplitude demonstrates a peak in the angular distribution of the cross sections. This peak, the so-called Thomas peak, was predicted by Thomas in a two-step interaction, classically, which could also be described through three-body quantum mechanical models. This work discusses a four-body quantum treatment of the charge transfer in ion-atom collisions, where two-step interactions illustrating a Thomas peak are emphasized. In addition, the Pauli exclusion principle is taken into account for the initial and final states as well as the operators. It will be demonstrated that there is a momentum condition for each two-step interaction to occur in a single charge transfer channel, where new classical interactions lead to the Thomas mechanism.

Experimental Evidence for Space-Charge Effects between Ions of the Same Mass-to-Charge in Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry

PubMed Central

Wong, Richard L.; Amster, I. Jonathan

2009-01-01

It is often stated that ions of the same mass-to-charge do not induce space-charge frequency shifts among themselves in an ion cyclotron resonance mass spectrometry measurement. Here, we demonstrate space-charge induced frequency shifts for ions of a single mass-to-charge. The monoisotopic atomic ion, Cs+, was used for this study. The measured frequency is observed to decrease linearly with an increase in the number of ions, as has been reported previously for space-charge effects between ions of different mass-to-charge. The frequency shift between ions of the same m/z value are compared to that induced between ions of different m/z value, and is found to be 7.5 times smaller. Control experiments were performed to ensure that the observed space-charge effects are not artifacts of the measurement or of experimental design. The results can be rationalized by recognizing that the electric forces between ions in a magnetic field conform to the weak form of the Newton's third law, where the action and reaction forces do not cancel exactly. PMID:19562102

Performing the Millikan experiment at the molecular scale: Determination of atomic Millikan-Thomson charges by computationally measuring atomic forces.

PubMed

Rogers, T Ryan; Wang, Feng

2017-10-28

An atomic version of the Millikan oil drop experiment is performed computationally. It is shown that for planar molecules, the atomic version of the Millikan experiment can be used to define an atomic partial charge that is free from charge flow contributions. We refer to this charge as the Millikan-Thomson (MT) charge. Since the MT charge is directly proportional to the atomic forces under a uniform electric field, it is the most relevant charge for force field developments. The MT charge shows good stability with respect to different choices of the basis set. In addition, the MT charge can be easily calculated even at post-Hartree-Fock levels of theory. With the MT charge, it is shown that for a planar water dimer, the charge transfer from the proton acceptor to the proton donor is about -0.052 e. While both planar hydrated cations and anions show signs of charge transfer, anions show a much more significant charge transfer to the hydration water than the corresponding cations. It might be important to explicitly model the ion charge transfer to water in a force field at least for the anions.

Photo ion spectrometer

DOEpatents

Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

1989-01-01

A charged particle spectrometer for performing ultrasensitive quantitative analysis of selected atomic components removed from a sample. Significant improvements in performing energy and angular refocusing spectroscopy are accomplished by means of a two dimensional structure for generating predetermined electromagnetic field boundary conditions. Both resonance and non-resonance ionization of selected neutral atomic components allow accumulation of increased chemical information. A multiplexed operation between a SIMS mode and a neutral atomic component ionization mode with EARTOF analysis enables comparison of chemical information from secondary ions and neutral atomic components removed from the sample. An electronic system is described for switching high level signals, such as SIMS signals, directly to a transient recorder and through a charge amplifier to the transient recorder for a low level signal pulse counting mode, such as for a neutral atomic component ionization mode.

Proceeding of the 18th Intl. Workshop on Inelastic Ion-Surface Collisions (IISC-18)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinhold, Carlos O; Krstic, Predrag S; Meyer, Fred W

2011-01-01

The main topics of this proceedings were: (1) Energy loss of particles at surfaces; (2) Scattering of atoms, ions, molecules and clusters; (3) Charge exchange between particles and surfaces; (4) Ion induced desorption, electronic and kinetic sputtering; (5) Defect formation, surface modification and nanostructuring; (6) Electron, photon and secondary ion emission due to particle impact on surfaces; (7) Sputtering, fragmentation, cluster and ion formation in SIMS and SNMS; (8) Cluster/molecular and highly charged ion beams; and (9) Laser induced desorption.

Ultracold collisions between Rb atoms and a Sr+ ion

NASA Astrophysics Data System (ADS)

Meir, Ziv; Sikorsky, Tomas; Ben-Shlomi, Ruti; Dallal, Yehonatan; Ozeri, Roee

2015-05-01

In last decade, a novel field emerged, in which ultracold atoms and ions in overlapping traps are brought into interaction. In contrast to the short ranged atom-atom interaction which scales as r-6, atom-ion potential persists for hundreds of μm's due to its lower power-law scaling - r-4. Inelastic collisions between the consistuents lead to spin and charge transfer and also to molecule formation. Elastic collisions control the energy transfer between the ion and the atoms. The study of collisions at the μK range has thus far been impeded by the effect of the ion's micromotion which limited collision energy to mK scale. Unraveling this limit will allow to investigate few partial wave and even S-wave collisions. Our system is capable of trapping Sr+ ions and Rb and Sr atoms and cooling them to their quantum ground state. Atoms and ions are trapped and cooled in separate chambers. Then, the atoms are transported using an optical conveyer belt to overlap the ions. In contrast to other experiments in this field where the atoms are used to sympathetic cool the ion, our system is also capable of ground state cooling the ion before immersing it into the atom cloud. By this method, we would be able to explore heating and cooling dynamics in the ultracold regime.

Genetics Home Reference: Gitelman syndrome

MedlinePlus

... syndrome is a kidney disorder that causes an imbalance of charged atoms (ions) in the body, including ... ions of potassium, magnesium, and calcium. The resulting imbalance of ions in the body underlies the major ...

Erosion rate diagnostics in ion thrusters using laser-induced fluorescence

NASA Technical Reports Server (NTRS)

Gaeta, C. J.; Matossian, J. N.; Turley, R. S.; Beattie, J. R.; Williams, J. D.; Williamson, W. S.

1993-01-01

We have used laser-induced fluorescence (LIF) to monitor the charge-exchange ion erosion of the molybdenum accelerator electrode in ion thrusters. This real-time, nonintrusive method was implemented by operating a 30cm-diam ring-cusp thruster using xenon propellant. With the thruster operating at a total power of 5 kW, laser radiation at a wavelength of 390 nm (corresponding to a ground state atomic transition of molybdenum) was directed through the extracted ion beam adjacent to the downstream surface of the molybdenum accelerator electrode. Molybdenum atoms, sputtered from this surface as a result of charge-exchange ion erosion, were excited by the laser radiation. The intensity of the laser-induced fluorescence radiation, which is proportional to the sputter rate of the molybdenum atoms, was measured and correlated with variations in thruster operating conditions such as accelerator electrode voltage, accelerator electrode current, and test facility background pressure. We also demonstrated that the LIF technique has sufficient sensitivity and spatial resolution to evaluate accelerator electrode lifetime in ground-based test facilities.

Extraction of highly charged ions from the Berlin Electron Beam Ion Trap for interactions with a gas target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, F.I.; Biedermann, C.; Radtke, R.

2006-03-15

Highly charged ions are extracted from the Berlin Electron Beam Ion Trap for investigations of charge exchange with a gas target. The classical over-the-barrier model for slow highly charged ions describes this process, whereby one or more electrons are captured from the target into Rydberg states of the ion. The excited state relaxes via a radiative cascade of the electron to ground energy. The cascade spectra are characteristic of the capture state. We investigate x-ray photons emitted as a result of interactions between Ar{sup 17+} ions at energies {<=}5q keV with Ar atoms. Of particular interest is the velocity dependencemore » of the angular momentum capture state l{sub c}.« less

Photo ion spectrometer

DOEpatents

Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

1989-01-01

A method and apparatus for extracting for quantitative analysis ions of selected atomic components of a sample. A lens system is configured to provide a slowly diminishing field region for a volume containing the selected atomic components, enabling accurate energy analysis of ions generated in the slowly diminishing field region. The lens system also enables focusing on a sample of a charged particle beam, such as an ion beam, along a path length perpendicular to the sample and extraction of the charged particles along a path length also perpendicular to the sample. Improvement of signal to noise ratio is achieved by laser excitation of ions to selected autoionization states before carrying out quantitative analysis. Accurate energy analysis of energetic charged particles is assured by using a preselected resistive thick film configuration disposed on an insulator substrate for generating predetermined electric field boundary conditions to achieve for analysis the required electric field potential. The spectrometer also is applicable in the fields of SIMS, ISS and electron spectroscopy.

Photo ion spectrometer

DOEpatents

Gruen, D.M.; Young, C.E.; Pellin, M.J.

1989-08-08

A method and apparatus are described for extracting for quantitative analysis ions of selected atomic components of a sample. A lens system is configured to provide a slowly diminishing field region for a volume containing the selected atomic components, enabling accurate energy analysis of ions generated in the slowly diminishing field region. The lens system also enables focusing on a sample of a charged particle beam, such as an ion beam, along a path length perpendicular to the sample and extraction of the charged particles along a path length also perpendicular to the sample. Improvement of signal to noise ratio is achieved by laser excitation of ions to selected auto-ionization states before carrying out quantitative analysis. Accurate energy analysis of energetic charged particles is assured by using a preselected resistive thick film configuration disposed on an insulator substrate for generating predetermined electric field boundary conditions to achieve for analysis the required electric field potential. The spectrometer also is applicable in the fields of SIMS, ISS and electron spectroscopy. 8 figs.

Experimental apparatus for overlapping a ground-state cooled ion with ultracold atoms

NASA Astrophysics Data System (ADS)

Meir, Ziv; Sikorsky, Tomas; Ben-shlomi, Ruti; Akerman, Nitzan; Pinkas, Meirav; Dallal, Yehonatan; Ozeri, Roee

2018-03-01

Experimental realizations of charged ions and neutral atoms in overlapping traps are gaining increasing interest due to their wide research application ranging from chemistry at the quantum level to quantum simulations of solid state systems. In this paper, we describe our experimental system in which we overlap a single ground-state cooled ion trapped in a linear Paul trap with a cloud of ultracold atoms such that both constituents are in the ?K regime. Excess micromotion (EMM) currently limits atom-ion interaction energy to the mK energy scale and above. We demonstrate spectroscopy methods and compensation techniques which characterize and reduce the ion's parasitic EMM energy to the ?K regime even for ion crystals of several ions. We further give a substantial review on the non-equilibrium dynamics which governs atom-ion systems. The non-equilibrium dynamics is manifested by a power law distribution of the ion's energy. We also give an overview on the coherent and non-coherent thermometry tools which can be used to characterize the ion's energy distribution after single to many atom-ion collisions.

The estimation of H-bond and metal ion-ligand interaction energies in the G-Quadruplex ⋯ Mn+ complexes

NASA Astrophysics Data System (ADS)

Mostafavi, Najmeh; Ebrahimi, Ali

2018-06-01

In order to characterize various interactions in the G-quadruplex ⋯ Mn+ (G-Q ⋯ Mn+) complexes, the individual H-bond (EHB) and metal ion-ligand interaction (EMO) energies have been estimated using the electron charge densities (ρs) calculated at the X ⋯ H (X = N and O) and Mn+ ⋯ O (Mn+ is an alkaline, alkaline earth and transition metal ion) bond critical points (BCPs) obtained from the atoms in molecules (AIM) analysis. The estimated values of EMO and EHB were evaluated using the structural parameters, results of natural bond orbital analysis (NBO), aromaticity indexes and atomic charges. The EMO value increase with the ratio of ionic charge to radius, e/r, where a linear correlation is observed between EMO and e/r (R = 0.97). Meaningful relationships are also observed between EMO and indexes used for aromaticity estimation. The ENH value is higher than EOH in the complexes; this is in complete agreement with the trend of N⋯Hsbnd N and O⋯Hsbnd N angles, the E (2) value of nN → σ*NH and nO → σ*NH interactions and the difference between the natural charges on the H-bonded atom and the hydrogen atom of guanine (Δq). In general, the O1MO2 angle becomes closer to 109.5° with the increase in EMO and decrease in EHB in the presence of metal ion.

Fast computation of high energy elastic collision scattering angle for electric propulsion plume simulation

NASA Astrophysics Data System (ADS)

Araki, Samuel J.

2016-11-01

In the plumes of Hall thrusters and ion thrusters, high energy ions experience elastic collisions with slow neutral atoms. These collisions involve a process of momentum exchange, altering the initial velocity vectors of the collision pair. In addition to the momentum exchange process, ions and atoms can exchange electrons, resulting in slow charge-exchange ions and fast atoms. In these simulations, it is particularly important to accurately perform computations of ion-atom elastic collisions in determining the plume current profile and assessing the integration of spacecraft components. The existing models are currently capable of accurate calculation but are not fast enough such that the calculation can be a bottleneck of plume simulations. This study investigates methods to accelerate an ion-atom elastic collision calculation that includes both momentum- and charge-exchange processes. The scattering angles are pre-computed through a classical approach with ab initio spin-orbit free potential and are stored in a two-dimensional array as functions of impact parameter and energy. When performing a collision calculation for an ion-atom pair, the scattering angle is computed by a table lookup and multiple linear interpolations, given the relative energy and randomly determined impact parameter. In order to further accelerate the calculations, the number of collision calculations is reduced by properly defining two cut-off cross-sections for the elastic scattering. In the MCC method, the target atom needs to be sampled; however, it is confirmed that initial target atom velocity does not play a significant role in typical electric propulsion plume simulations such that the sampling process is unnecessary. With these implementations, the computational run-time to perform a collision calculation is reduced significantly compared to previous methods, while retaining the accuracy of the high fidelity models.

The design of the Spectrometer Ring at the HIAF

NASA Astrophysics Data System (ADS)

Wu, B.; Yang, J. C.; Xia, J. W.; Yan, X. L.; Hu, X. J.; Mao, L. J.; Sheng, L. N.; Wu, J. X.; Yin, D. Y.; Chai, W. P.; Shen, G. D.; Ge, W. W.; Wang, G.; Zhao, H.; Ruan, S.; Ma, X. W.; Wang, M.; Litvinov, S.; Wen, W. Q.; Chen, X. C.; Chen, R. J.; Tang, M. T.; Wu, W.; Luo, C.; Zhao, T. C.; Shi, C. F.; Fu, X.; Liu, J.; Liang, L.

2018-02-01

The Spectrometer Ring (SRing) is an essential part of the High Intensity heavy-ion Accelerator Facility project (HIAF) in China. It is designed as a multi-functional experimental storage ring, which will be able to operate in three ion optical operation modes. The SRing will be used as a time-of-flight mass spectrometer for short-lived, especially neutron-rich nuclei. It will also be used to collect and cool Rare Isotope Beams (RIBs) or highly-charged stable ion beams for nuclear and atomic physics experiments. The design magnetic rigidity is in the range 1.5 to 15 Tm. The beam cooling system consists of stochastic cooling and electron cooling devices. With a help of an electron cooler, stored ions will be decelerated to a minimum energy of 30 MeV/u by RF cavities. The extraction system of the SRing will allow cooled ion beams to be extracted to an external target for further ion manipulations or reaction experiments. The general ion optics design and technical requirements of SRing subsystems are presented and discussed in this paper.

The Development Of New Space Charge Compensation Methods For Multi-Components Ion Beam Extracted From ECR Ion Source at IMP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, L.; Zhao, H.W.; Cao, Y.

2005-03-15

Two new space charge compensation methods developed in IMP are discussed in this paper. There are negative high voltage electrode method (NHVEM) and electronegative charge gas method (EGM). Some valuable experimental data have been achieved, especially using electronegative gas method in O6+ and O7+ dramatic and stable increasing of ion current was observed.

Paving the way to nanoionics: atomic origin of barriers for ionic transport through interfaces.

PubMed

Frechero, M A; Rocci, M; Sánchez-Santolino, G; Kumar, Amit; Salafranca, J; Schmidt, Rainer; Díaz-Guillén, M R; Durá, O J; Rivera-Calzada, A; Mishra, R; Jesse, Stephen; Pantelides, S T; Kalinin, Sergei V; Varela, M; Pennycook, S J; Santamaria, J; Leon, C

2015-12-17

The blocking of ion transport at interfaces strongly limits the performance of electrochemical nanodevices for energy applications. The barrier is believed to arise from space-charge regions generated by mobile ions by analogy to semiconductor junctions. Here we show that something different is at play by studying ion transport in a bicrystal of yttria (9% mol) stabilized zirconia (YSZ), an emblematic oxide ion conductor. Aberration-corrected scanning transmission electron microscopy (STEM) provides structure and composition at atomic resolution, with the sensitivity to directly reveal the oxygen ion profile. We find that Y segregates to the grain boundary at Zr sites, together with a depletion of oxygen that is confined to a small length scale of around 0.5 nm. Contrary to the main thesis of the space-charge model, there exists no evidence of a long-range O vacancy depletion layer. Combining ion transport measurements across a single grain boundary by nanoscale electrochemical strain microscopy (ESM), broadband dielectric spectroscopy measurements, and density functional calculations, we show that grain-boundary-induced electronic states act as acceptors, resulting in a negatively charged core. Besides the possible effect of the modified chemical bonding, this negative charge gives rise to an additional barrier for ion transport at the grain boundary.

Paving the way to nanoionics: Atomic origin of barriers for ionic transport through interfaces

DOE PAGES

Frechero, M. A.; Rocci, M.; Sanchez-Santolino, G.; ...

2015-12-17

The blocking of ion transport at interfaces strongly limits the performance of electrochemical nanodevices for energy applications. The barrier is believed to arise from space-charge regions generated by mobile ions by analogy to semiconductor junctions. Here we show that something different is at play by studying ion transport in a bicrystal of yttria (9% mol) stabilized zirconia (YSZ), an emblematic oxide ion conductor. Aberration-corrected scanning transmission electron microscopy (STEM) provides structure and composition at atomic resolution, with the sensitivity to directly reveal the oxygen ion profile. We find that Y segregates to the grain boundary at Zr sites, together withmore » a depletion of oxygen that is confined to a small length scale of around 0.5 nm. Contrary to the main thesis of the space-charge model, there exists no evidence of a long-range O vacancy depletion layer. Combining ion transport measurements across a single grain boundary by nanoscale electrochemical strain microscopy (ESM), broadband dielectric spectroscopy measurements, and density functional calculations, we show that grain-boundary-induced electronic states act as acceptors, resulting in a negatively charged core. In conclusion, besides the possible effect of the modified chemical bonding, this negative charge gives rise to an additional barrier for ion transport at the grain boundary.« less

Self-Consistent Determination of Atomic Charges of Ionic Liquid through a Combination of Molecular Dynamics Simulation and Density Functional Theory.

PubMed

Ishizuka, Ryosuke; Matubayasi, Nobuyuki

2016-02-09

A self-consistent scheme is developed to determine the atomic partial charges of ionic liquid. Molecular dynamics (MD) simulation was conducted to sample a set of ion configurations, and these configurations were subject to density functional theory (DFT) calculations to determine the partial charges. The charges were then averaged and used as inputs for the subsequent MD simulation, and MD and DFT calculations were repeated until the MD results are not altered any more. We applied this scheme to 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide ([C1mim][NTf2]) and investigated its structure and dynamics as a function of temperature. At convergence, the average ionic charges were ±0.84 e at 350 K due to charge transfer among ions, where e is the elementary charge, while the reduced ionic charges do not affect strongly the density of [C1mim][NTf2] and radial distribution function. Instead, major effects are found on the energetics and dynamics, with improvements of the overestimated heat of vaporization and the too slow motions of ions observed in MD simulations using commonly used force fields.

HITRAP: A Facility for Experiments with Trapped Highly Charged Ions

NASA Astrophysics Data System (ADS)

Quint, W.; Dilling, J.; Djekic, S.; Häffner, H.; Hermanspahn, N.; Kluge, H.-J.; Marx, G.; Moore, R.; Rodriguez, D.; Schönfelder, J.; Sikler, G.; Valenzuela, T.; Verdú, J.; Weber, C.; Werth, G.

2001-01-01

HITRAP is a planned ion trap facility for capturing and cooling of highly charged ions produced at GSI in the heavy-ion complex of the UNILAC-SIS accelerators and the ESR storage ring. In this facility heavy highly charged ions up to uranium will be available as bare nuclei, hydrogen-like ions or few-electron systems at low temperatures. The trap for receiving and studying these ions is designed for operation at extremely high vacuum by cooling to cryogenic temperatures. The stored highly charged ions can be investigated in the trap itself or can be extracted from the trap at energies up to about 10 keV/q. The proposed physics experiments are collision studies with highly charged ions at well-defined low energies (eV/u), high-accuracy measurements to determine the g-factor of the electron bound in a hydrogen-like heavy ion and the atomic binding energies of few-electron systems, laser spectroscopy of HFS transitions and X-ray spectroscopy.

Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade.

PubMed

Kolmogorov, A; Atoian, G; Davydenko, V; Ivanov, A; Ritter, J; Stupishin, N; Zelenski, A

2014-02-01

The RHIC polarized H(-) ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

PubMed

Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

2015-05-28

Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and hence, also affecting the location of the Ce(III) cations and the structure of the TM13 clusters.

Surface and material analytics based on Dresden-EBIS platform technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, M., E-mail: mike.schmidt@dreebit.com; König, J., E-mail: mike.schmidt@dreebit.com; Bischoff, L.

2015-01-09

Nowadays widely used mass spectrometry systems utilize energetic ions hitting a sample and sputter material from the surface of a specimen. The generated secondary ions are separated and detected with high mass resolution to determine the target materials constitution. Based on this principle, we present an alternative approach implementing a compact Electron Beam Ion Source (EBIS) in combination with a Liquid Metal Ion Source (LMIS). An LMIS can deliver heavy elements which generate high sputter yields on a target surface. More than 90% of this sputtered material consists of mono- and polyatomic neutrals. These particles are able to penetrate themore » magnetic field of an EBIS and they will be ionized within the electron beam. A broad spectrum of singly up to highly charged ions can be extracted depending on the operation conditions. Polyatomic ions will decay during the charge-up process. A standard bending magnet or a Wien filter is used to separate the different ion species due to their mass-to-charge ratio. Using different charge states of ions as it is common with EBIS it is also possible to resolve interfering charge-to-mass ratios of only singly charged ions. Different setups for the realization of feeding the electron beam with sputtered atoms of solids will be presented and discussed. As an example the analysis of a copper surface is used to show high-resolution spectra with low background noise. Individual copper isotopes and clusters with different isotope compositions can be resolved at equal atomic numbers. These results are a first step for the development of a new compact low-cost and high-resolution mass spectrometry system. In a more general context, the described technique demonstrates an efficient method for feeding an EBIS with atoms of nearly all solid elements from various solid target materials. The new straightforward design of the presented setup should be of high interest for a broad range of applications in materials research as well as for applications connected to analyzing the biosphere, hydrosphere, lithosphere, cosmosphere and technosphere.« less

Photo ion spectrometer

DOEpatents

Gruen, D.M.; Young, C.E.; Pellin, M.J.

1989-12-26

A charged particle spectrometer is described for performing ultrasensitive quantitative analysis of selected atomic components removed from a sample. Significant improvements in performing energy and angular refocusing spectroscopy are accomplished by means of a two dimensional structure for generating predetermined electromagnetic field boundary conditions. Both resonance and non-resonance ionization of selected neutral atomic components allow accumulation of increased chemical information. A multiplexed operation between a SIMS mode and a neutral atomic component ionization mode with EARTOF analysis enables comparison of chemical information from secondary ions and neutral atomic components removed from the sample. An electronic system is described for switching high level signals, such as SIMS signals, directly to a transient recorder and through a charge amplifier to the transient recorder for a low level signal pulse counting mode, such as for a neutral atomic component ionization mode. 12 figs.

Reaction kinetics of a kHz-driven atmospheric pressure plasma with humid air impurities

NASA Astrophysics Data System (ADS)

Murakami, T.; Algwari, Q. Th.; Niemi, K.; Gans, T.; O'Connell, D.; Graham, W. G.

2013-09-01

Atmospheric-pressure plasma jets (APPJs) have been gaining attention because of their great potential in bio-plasma applications. It is important to know the complex chemical kinetics of the reactive multi-species plasma. This is a study starting to address this by using a 0D time-dependent global simulation (comprising 1050 elementary reactions among 59 specie) of kHz-driven (20 kHz) APPJ with a helium-based oxygen-mixture (0.5%) with ambient humid air impurity. The present model is initiated from time dependent measurements and estimates of the basic plasma properties. The dominant neutral reactive species are reactive oxygen species and atomic hydrogen. The positive and negative oxygen ions and electrons are the most pronounced charged species. While most of the neutral reactive species are only weakly modulated at the driving frequency, the atomic oxygen metastables and atomic nitrogen metastables are strongly modulated. So are also the electrons and most of the positive and negative ions, but some are not, as will be discussed. This work was supported by KAKENHI (MEXT 24110704) and (JSPS 24561054),and UK EPSRC through a Career Acceleration Fellowship (EP/H003797/1) and Science and Innovation Award (EP/D06337X/1).

One-dimension modeling on the parallel-plate ion extraction process based on a non-electron-equilibrium fluid model

NASA Astrophysics Data System (ADS)

Li, He-Ping; Chen, Jian; Guo, Heng; Jiang, Dong-Jun; Zhou, Ming-Sheng; Department of Engineering Physics Team

2017-10-01

Ion extraction from a plasma under an externally applied electric field involve multi-particle and multi-field interactions, and has wide applications in the fields of materials processing, etching, chemical analysis, etc. In order to develop the high-efficiency ion extraction methods, it is indispensable to establish a feasible model to understand the non-equilibrium transportation processes of the charged particles and the evolutions of the space charge sheath during the extraction process. Most of the previous studies on the ion extraction process are mainly based on the electron-equilibrium fluid model, which assumed that the electrons are in the thermodynamic equilibrium state. However, it may lead to some confusions with neglecting the electron movement during the sheath formation process. In this study, a non-electron-equilibrium model is established to describe the transportation of the charged particles in a parallel-plate ion extraction process. The numerical results show that the formation of the Child-Langmuir sheath is mainly caused by the charge separation. And thus, the sheath shielding effect will be significantly weakened if the charge separation is suppressed during the extraction process of the charged particles.

K-shell X-ray transition energies of multi-electron ions of silicon and sulfur

NASA Astrophysics Data System (ADS)

Beiersdorfer, P.; Brown, G. V.; Hell, N.; Santana, J. A.

2017-10-01

Prompted by the detection of K-shell absorption or emission features in the spectra of plasma surrounding high mass X-ray binaries and black holes, recent measurements using the Livermore electron beam ion trap have focused on the energies of the n = 2 to n = 1 K-shell transitions in the L-shell ions of lithiumlike through fluorinelike silicon and sulfur. In parallel, we have made calculations of these transitions using the Flexible Atomic Code and the multi-reference Møller-Plesset (MRMP) atomic physics code. Using this code we have attempted to produce sets of theoretical atomic data with spectroscopic accuracy for all the L-shell ions of silicon and sulfur. We present results of our calculations for oxygenlike and fluorinelike silicon and compare them to the recent electron beam ion trap measurements as well as previous calculations.

K-shell X-ray transition energies of multi-electron ions of silicon and sulfur

DOE PAGES

Beiersdorfer, P.; Brown, G. V.; Hell, N.; ...

2017-04-20

Prompted by the detection of K-shell absorption or emission features in the spectra of plasma surrounding high mass X-ray binaries and black holes, recent measurements using the Livermore electron beam ion trap have focused on the energies of the n = 2 to n = 1 K-shell transitions in the L-shell ions of lithiumlike through fluorinelike silicon and sulfur. In parallel, we have made calculations of these transitions using the Flexible Atomic Code and the multi-reference Møller-Plesset (MRMP) atomic physics code. Using this code we have attempted to produce sets of theoretical atomic data with spectroscopic accuracy for all themore » L-shell ions of silicon and sulfur. Here, we present results of our calculations for oxygenlike and fluorinelike silicon and compare them to the recent electron beam ion trap measurements as well as previous calculations.« less

Z-dependence of mean excitation energies for second and third row atoms and their ions

NASA Astrophysics Data System (ADS)

Sauer, Stephan P. A.; Sabin, John R.; Oddershede, Jens

2018-05-01

All mean excitation energies for second and third row atoms and their ions are calculated in the random-phase approximation using large basis sets. To a very good approximation, it turns out that mean excitation energies within an isoelectronic series are a quadratic function of the nuclear charge. It is demonstrated that this behavior is linked to the fact that the contributions from continuum electronic states give the dominate contributions to the mean excitation energies and that these contributions for atomic ions appear hydrogen-like. We argue that this finding may present a method to get a first estimate of mean excitation energies also for other non-relativistic atomic ions.

Conducting ion tracks generated by charge-selected swift heavy ions

NASA Astrophysics Data System (ADS)

Gupta, Srashti; Gehrke, H. G.; Krauser, J.; Trautmann, C.; Severin, D.; Bender, M.; Rothard, H.; Hofsäss, H.

2016-08-01

Conducting ion tracks in tetrahedral amorphous carbon (ta-C) thin films were generated by irradiation with swift heavy ions of well-defined charge state. The conductivity of tracks and the surface topography of the films, showing characteristic hillocks at each track position, were investigated using conductive atomic force microscopy measurements. The dependence of track conductivity and hillock size on the charge state of the ions was studied using 4.6 MeV/u Pb ions of charge state 53+, 56+ and 60+ provided by GANIL, as well as 4.8 MeV/u Bi and Au ions of charge state from 50+ to 61+ and 4.2 MeV/u 238U ions in equilibrium charge state provided by UNILAC of GSI. For the charge state selection at GSI, an additional stripper-foil system was installed at the M-branch that now allows routine irradiations with ions of selected charge states. The conductivity of tracks in ta-C increases significantly when the charge state increases from 51+ to 60+. However, the conductivity of individual tracks on the same sample still shows large variations, indicating that tracks formed in ta-C are either inhomogeneous or the conductivity is limited by the interface between ion track and Si substrate.

Charge radii and electromagnetic moments of At-211195

NASA Astrophysics Data System (ADS)

Cubiss, J. G.; Barzakh, A. E.; Seliverstov, M. D.; Andreyev, A. N.; Andel, B.; Antalic, S.; Ascher, P.; Atanasov, D.; Beck, D.; Bieroń, J.; Blaum, K.; Borgmann, Ch.; Breitenfeldt, M.; Capponi, L.; Cocolios, T. E.; Day Goodacre, T.; Derkx, X.; De Witte, H.; Elseviers, J.; Fedorov, D. V.; Fedosseev, V. N.; Fritzsche, S.; Gaffney, L. P.; George, S.; Ghys, L.; Heßberger, F. P.; Huyse, M.; Imai, N.; Kalaninová, Z.; Kisler, D.; Köster, U.; Kowalska, M.; Kreim, S.; Lane, J. F. W.; Liberati, V.; Lunney, D.; Lynch, K. M.; Manea, V.; Marsh, B. A.; Mitsuoka, S.; Molkanov, P. L.; Nagame, Y.; Neidherr, D.; Nishio, K.; Ota, S.; Pauwels, D.; Popescu, L.; Radulov, D.; Rapisarda, E.; Revill, J. P.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Sandhu, K.; Schweikhard, L.; Sels, S.; Truesdale, V. L.; Van Beveren, C.; Van den Bergh, P.; Wakabayashi, Y.; Van Duppen, P.; Wendt, K. D. A.; Wienholtz, F.; Whitmore, B. W.; Wilson, G. L.; Wolf, R. N.; Zuber, K.

2018-05-01

Hyperfine-structure parameters and isotope shifts of At-211195 have been measured for the first time at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy method. The hyperfine structures of isotopes were recorded using a triad of experimental techniques for monitoring the photo-ion current. The Multi-Reflection Time-of-Flight Mass Spectrometer, in connection with a high-resolution electron multiplier, was used as an ion-counting setup for isotopes that either were affected by strong isobaric contamination or possessed a long half-life; the ISOLDE Faraday cups were used for cases with high-intensity beams; and the Windmill decay station was used for short-lived, predominantly α -decaying nuclei. The electromagnetic moments and changes in the mean-square charge radii of the astatine nuclei have been extracted from the measured hyperfine-structure constants and isotope shifts. This was only made possible by dedicated state-of-the-art large-scale atomic computations of the electronic factors and the specific mass shift of atomic transitions in astatine that are needed for these extractions. By comparison with systematics, it was possible to assess the reliability of the results of these calculations and their ascribed uncertainties. A strong deviation in the ground-state mean-square charge radii of the lightest astatine isotopes, from the trend of the (spherical) lead isotopes, is interpreted as the result of an onset of deformation. This behavior bears a resemblance to the deviation observed in the isotonic polonium isotopes. Cases for shape coexistence have been identified in At,199197, for which a significant difference in the charge radii for ground (9 /2- ) and isomeric (1 /2+ ) states has been observed.

Numerical quasi-linear study of the critical ionization velocity phenomenon

NASA Technical Reports Server (NTRS)

Moghaddam-Taaheri, E.; Goertz, C. K.

1993-01-01

The critical ionization velocity (CIV) for a neutral barium (Ba) gas cloud moving across the static magnetic field is studied numerically using quasi-linear equations and a parameter range which is typical for the shaped-charge Ba gas release experiments in space. For consistency the charge exchange between the background oxygen ions and neutral atoms and its reverse process, as well as the excitation of the neutral Ba atoms, are included. The numerical results indicate that when the ionization rate due to CIV becomes comparable to the charge exchange rate the energy lost to the ionization and excitation collisions by the superthermal electrons exceeds the energy gain from the waves that are excited by the ion beam. This results in a CIV yield less than the yield by the charge exchange process.

Charge exchange collisions of slow C6 + with atomic and molecular H

NASA Astrophysics Data System (ADS)

Saha, Bidhan C.; Guevara, Nicolais L.; Sabin, John R.; Deumens, Erik; Öhrn, Yngve

2016-04-01

Charge exchange in collisions of C6+ ions with H and H2 is investigated theoretically at projectile energies 0.1 < E < 10 keV/amu, using electron nuclear dynamics (END) - a semi-classical approximation which not only includes electron translation factors for avoiding spurious couplings but also employs full dynamical trajectories to treat nuclear motions. Both the total and partial cross sections are reported for the collision of C6+ ions with atomic and molecular hydrogen. A comparison with other theoretical and experimental results shows, in general good agreement except at very low energy, considered here. For H2, the one- and two-electron charge exchange cross sections are calculated and compared with other theoretical and experimental results. Small but non-negligible isotope effects are found at the lowest energy studied in the charge transfer of C6+ with H. In low energy region, it is observed that H2 has larger isotope effects than H atom due to the polarizability effect which is larger than the mass effect.

Numerical simulation of ion charge breeding in electron beam ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, L., E-mail: zhao@far-tech.com; Kim, Jin-Soo

2014-02-15

The Electron Beam Ion Source particle-in-cell code (EBIS-PIC) tracks ions in an EBIS electron beam while updating electric potential self-consistently and atomic processes by the Monte Carlo method. Recent improvements to the code are reported in this paper. The ionization module has been improved by using experimental ionization energies and shell effects. The acceptance of injected ions and the emittance of extracted ion beam are calculated by extending EBIS-PIC to the beam line transport region. An EBIS-PIC simulation is performed for a Cs charge-breeding experiment at BNL. The charge state distribution agrees well with experiments, and additional simulation results ofmore » radial profiles and velocity space distributions of the trapped ions are presented.« less

Multiphoton ionization of many-electron atoms and highly-charged ions in intense laser fields: a relativistic time-dependent density functional theory approach

NASA Astrophysics Data System (ADS)

Tumakov, Dmitry A.; Telnov, Dmitry A.; Maltsev, Ilia A.; Plunien, Günter; Shabaev, Vladimir M.

2017-10-01

We develop an efficient numerical implementation of the relativistic time-dependent density functional theory (RTDDFT) to study multielectron highly-charged ions subject to intense linearly-polarized laser fields. The interaction with the electromagnetic field is described within the electric dipole approximation. The resulting time-dependent relativistic Kohn-Sham (RKS) equations possess an axial symmetry and are solved accurately and efficiently with the help of the time-dependent generalized pseudospectral method. As a case study, we calculate multiphoton ionization probabilities of the neutral argon atom and argon-like xenon ion. Relativistic effects are assessed by comparison of our present results with existing non-relativistic data.

A combined rocket-borne and ground-based study of the sodium layer and charged dust in the upper mesosphere

NASA Astrophysics Data System (ADS)

Plane, John M. C.; Saunders, Russell W.; Hedin, Jonas; Stegman, Jacek; Khaplanov, Misha; Gumbel, Jörg; Lynch, Kristina A.; Bracikowski, Phillip J.; Gelinas, Lynette J.; Friedrich, Martin; Blindheim, Sandra; Gausa, Michael; Williams, Bifford P.

2014-10-01

The Hotel Payload 2 rocket was launched on January 31st 2008 at 20.14 LT from the Andøya Rocket Range in northern Norway (69.31° N, 16.01° E). Measurements in the 75-105 km region of atomic O, negatively-charged dust, positive ions and electrons with a suite of instruments on the payload were complemented by lidar measurements of atomic Na and temperature from the nearby ALOMAR observatory. The payload passed within 2.58 km of the lidar at an altitude of 90 km. A series of coupled models is used to explore the observations, leading to two significant conclusions. First, the atomic Na layer and the vertical profiles of negatively-charged dust (assumed to be meteoric smoke particles), electrons and positive ions, can be modelled using a self-consistent meteoric input flux. Second, electronic structure calculations and Rice-Ramsperger-Kassel-Markus theory are used to show that even small Fe-Mg-silicates are able to attach electrons rapidly and form stable negatively-charged particles, compared with electron attachment to O2 and O3. This explains the substantial electron depletion between 80 and 90 km, where the presence of atomic O at concentrations in excess of 1010 cm-3 prevents the formation of stable negative ions.

QED theory of multiphoton transitions in atoms and ions

NASA Astrophysics Data System (ADS)

Zalialiutdinov, Timur A.; Solovyev, Dmitry A.; Labzowsky, Leonti N.; Plunien, Günter

2018-03-01

This review surveys the quantum theory of electromagnetic radiation for atomic systems. In particular, a review of current theoretical studies of multiphoton processes in one and two-electron atoms and highly charged ions is provided. Grounded on the quantum electrodynamics description the multiphoton transitions in presence of cascades, spin-statistic behaviour of equivalent photons and influence of external electric fields on multiphoton in atoms and anti-atoms are discussed. Finally, the nonresonant corrections which define the validity of the concept of the excited state energy levels are introduced.

Halogeno-substituted 2-aminobenzoic acid derivatives for negative ion fragmentation studies of N-linked carbohydrates.

PubMed

Harvey, David J

2005-01-01

Negative ion electrospray mass spectra of high-mannose N-linked glycans derivatised with 2-aminobenzoic acids and ionised from solutions containing ammonium hydroxide gave prominent [M-H](-) ions accompanied by weaker [M-2H](2-) ions. Fragmentation of both types of ions gave prominent singly charged glycosidic cleavage ions containing the derivatised reducing terminus and ions from the non-reducing terminus that appeared to be products of cross-ring cleavages. Differentiation of these two groups of ions was conveniently achieved in a single spectrum by use of chloro- or bromo-substituted benzoic acids in order to label ions containing the derivative with an atom with a distinctive isotope pattern. Fragmentation of the doubly charged ions gave more abundant fragments, both singly and doubly charged, than did fragmentation of the singly charged ions, but information of chain branching was masked by the appearance of prominent ions produced by internal cleavages. Copyright (c) 2005 John Wiley & Sons, Ltd.

Level-energy-dependent mean velocities of excited tungsten atoms sputtered by krypton-ion bombardment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nogami, Keisuke; Sakai, Yasuhiro; Mineta, Shota

2015-11-15

Visible emission spectra were acquired from neutral atoms sputtered by 35–60 keV Kr{sup +} ions from a polycrystalline tungsten surface. Mean velocities of excited tungsten atoms in seven different 6p states were also obtained via the dependence of photon intensities on the distance from the surface. The average velocities parallel to the surface normal varied by factors of 2–4 for atoms in the different 6p energy levels. However, they were almost independent of the incident ion kinetic energy. The 6p-level energy dependence indicated that the velocities of the excited atoms were determined by inelastic processes that involve resonant charge exchange.

Ionic Impurity in a Bose-Einstein Condensate at Submicrokelvin Temperatures

NASA Astrophysics Data System (ADS)

Kleinbach, K. S.; Engel, F.; Dieterle, T.; Löw, R.; Pfau, T.; Meinert, F.

2018-05-01

Rydberg atoms immersed in a Bose-Einstein condensate interact with the quantum gas via electron-atom and ion-atom interaction. To suppress the typically dominant electron-neutral interaction, Rydberg states with a principal quantum number up to n =190 are excited from a dense and tightly trapped micron-sized condensate. This allows us to explore a regime where the Rydberg orbit exceeds the size of the atomic sample by far. In this case, a detailed line shape analysis of the Rydberg excitation spectrum provides clear evidence for ion-atom interaction at temperatures well below a microkelvin. Our results may open up ways to enter the quantum regime of ion-atom scattering for the exploration of charged quantum impurities and associated polaron physics.

V. S. Lebedev and I. L. Beigman, Physics of Highly Excited Atoms and Ions

NASA Astrophysics Data System (ADS)

Mewe, R.

1999-07-01

This book contains a comprehensive description of the basic principles of the theoretical spectroscopy and experimental spectroscopic diagnostics of Rydberg atoms and ions, i.e., atoms in highly excited states with a very large principal quantum number (n≫1). Rydberg atoms are characterized by a number of peculiar physical properties as compared to atoms in the ground or a low excited state. They have a very small ionization potential (∝1/n2), the highly excited electron has a small orbital velocity (∝1/n), the radius (∝n2) is very large, the excited electron has a long orbital period (∝n3), and the radiation lifetime is very long (∝n3-5). At the same time the R. atom is very sensitive to perturbations from external fields in collisions with charged and neutral targets. In recent years, R. atoms have been observed in laboratory and cosmic conditions for n up to ˜1000, which means that the size amounts to about 0.1 mm, ˜106 times that of an atom in the ground state. The scope of this monograph is to familiarize the reader with today's approaches and methods for describing isolated R. atoms and ions, radiative transitions between highly excited states, and photoionization and photorecombination processes. The authors present a number of efficient methods for describing the structure and properties of R. atoms and calculating processes of collisions with neutral and charged particles as well as spectral-line broadening and shift of Rydberg atomic series in gases, cool and hot plasmas in laboratories and in astrophysical sources. Particular attention is paid to a comparison of theoretical results with available experimental data. The book contains 9 chapters. Chapter 1 gives an introduction to the basic properties of R. atoms (ions), Chapter 2 is devoted to an account of general methods describing an isolated Rydberg atom. Chapter 3 is focussed on the recent achievements in calculations of form factors and dipole matrix elements of different types of bound-bound and bound-free radiative transitions. Chapter 4 concentrates on the formulation of basic theoretical methods and physical approaches to collisions involving R. atoms. Chapters 5 to 8 contain a systematic description of major directions and modern techniques in the collision theory of R. atoms and ions with atoms, molecules, electrons, and ions. Finally, Chapter 9 deals with the spectral-line broadening and shift of R. atomic series induced by collisions with neutral and charged particles. A subject index of four pages and 250 references are given. This monograph will be a basic tool and reference for all scientists working in the fields of plasma physics, spectroscopy, physics of electronic and atomic collisions, as well as astrophysics, radio astronomy, and space physics.

The Los Alamos suite of relativistic atomic physics codes

DOE PAGES

Fontes, C. J.; Zhang, H. L.; Jr, J. Abdallah; ...

2015-05-28

The Los Alamos SuitE of Relativistic (LASER) atomic physics codes is a robust, mature platform that has been used to model highly charged ions in a variety of ways. The suite includes capabilities for calculating data related to fundamental atomic structure, as well as the processes of photoexcitation, electron-impact excitation and ionization, photoionization and autoionization within a consistent framework. These data can be of a basic nature, such as cross sections and collision strengths, which are useful in making predictions that can be compared with experiments to test fundamental theories of highly charged ions, such as quantum electrodynamics. The suitemore » can also be used to generate detailed models of energy levels and rate coefficients, and to apply them in the collisional-radiative modeling of plasmas over a wide range of conditions. Such modeling is useful, for example, in the interpretation of spectra generated by a variety of plasmas. In this work, we provide a brief overview of the capabilities within the Los Alamos relativistic suite along with some examples of its application to the modeling of highly charged ions.« less

IBEX-lo Sky Maps of Secondary Interstellar Neutrals Helium and Oxygen

NASA Astrophysics Data System (ADS)

Kucharek, H.; Isenberg, P. A.; Jeewoo, P.; Kubiak, M. A.; Bzowski, M.

2017-12-01

There are several populations of heliospheric energetic neutral atoms (ENAs) generated at the various heliospheric interfaces, the inner heliosheath, outer heliosheath (OHS), and the termination shock (TS). Depending on where and how these ENAs are generated, they belong to different energy regimes. While interstellar neutral (ISN) particles flow through the heliospheric boundary is mostly unimpeded, a substantial fraction of ISN H and O is filtered through charge exchange with ambient plasma ions before reaching the TS. Secondary ISN atoms are generated by the charge exchange reaction between primary ISN atoms and interstellar ions in the outer heliosheath, forming walls of H and O in front of the heliopause (HP). The flowing interstellar plasma encounters the heliopause as an obstacle, which deflects the flow. Thus, secondary neutrals measured at 1 AU carry information about the deflected interstellar plasma and the shape of the heliopause that causes the deflection. Due to very different magnitudes of charge exchange cross sections, the main source of the secondary He is charge exchange with the OHS He+, while that of the secondary O is the charge exchange between interstellar O+ and the OHS H. Therefore, the oxygen results are drastically different from those of helium. Interstellar O+ ions behave in principle like the He+ particles with an over-density due to the plasma deceleration. The high density decelerated oxygen ions just upwind of the heliopause encounter an over-density in neutral hydrogen, the hydrogen wall, allowing frequent charge exchange that produce slow neutral oxygen atoms forming the oxygen wall. Thus, the distribution in the sky maps of secondary He and O carries information on the shape as well as the structures in front of it. To investigate the secondary component of the interstellar neutral in detail we have distinguish between the two secondary component's. We engaged theory and simulations for the primary and secondary components to determine differences of between measurements and model predicted data.

Near-threshold photoionization of hydrogenlike uranium studied in ion-atom collisions via the time-reversed process.

PubMed

Stöhlker, T; Ma, X; Ludziejewski, T; Beyer, H F; Bosch, F; Brinzanescu, O; Dunford, R W; Eichler, J; Hagmann, S; Ichihara, A; Kozhuharov, C; Krämer, A; Liesen, D; Mokler, P H; Stachura, Z; Swiat, P; Warczak, A

2001-02-05

Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold.

Improved Barrier Properties in Flexible Plastic Substrates

DTIC Science & Technology

2009-01-01

layer 2:1 sandwich is required to balance this charge deficit. The extra charge is provided by a layer of large cations, usually potassium or sodium...ions (K+).32,30 Each of the potassium ions in this interiayer is shared among 12 oxygen atoms and the electrostatic force between the potassium ion...layer. Potassium • Aluminum • Silicon • Oxygen {-* Hydroxyl pair b axfs" This tabulation giving the layer by layer population of elements

Charge-transfer modified embedded atom method dynamic charge potential for Li-Co-O system

NASA Astrophysics Data System (ADS)

Kong, Fantai; Longo, Roberto C.; Liang, Chaoping; Nie, Yifan; Zheng, Yongping; Zhang, Chenxi; Cho, Kyeongjae

2017-11-01

To overcome the limitation of conventional fixed charge potential methods for the study of Li-ion battery cathode materials, a dynamic charge potential method, charge-transfer modified embedded atom method (CT-MEAM), has been developed and applied to the Li-Co-O ternary system. The accuracy of the potential has been tested and validated by reproducing a variety of structural and electrochemical properties of LiCoO2. A detailed analysis on the local charge distribution confirmed the capability of this potential for dynamic charge modeling. The transferability of the potential is also demonstrated by its reliability in describing Li-rich Li2CoO2 and Li-deficient LiCo2O4 compounds, including their phase stability, equilibrium volume, charge states and cathode voltages. These results demonstrate that the CT-MEAM dynamic charge potential could help to overcome the challenge of modeling complex ternary transition metal oxides. This work can promote molecular dynamics studies of Li ion cathode materials and other important transition metal oxides systems that involve complex electrochemical and catalytic reactions.

Charge-transfer modified embedded atom method dynamic charge potential for Li-Co-O system.

PubMed

Kong, Fantai; Longo, Roberto C; Liang, Chaoping; Nie, Yifan; Zheng, Yongping; Zhang, Chenxi; Cho, Kyeongjae

2017-11-29

To overcome the limitation of conventional fixed charge potential methods for the study of Li-ion battery cathode materials, a dynamic charge potential method, charge-transfer modified embedded atom method (CT-MEAM), has been developed and applied to the Li-Co-O ternary system. The accuracy of the potential has been tested and validated by reproducing a variety of structural and electrochemical properties of LiCoO 2 . A detailed analysis on the local charge distribution confirmed the capability of this potential for dynamic charge modeling. The transferability of the potential is also demonstrated by its reliability in describing Li-rich Li 2 CoO 2 and Li-deficient LiCo 2 O 4 compounds, including their phase stability, equilibrium volume, charge states and cathode voltages. These results demonstrate that the CT-MEAM dynamic charge potential could help to overcome the challenge of modeling complex ternary transition metal oxides. This work can promote molecular dynamics studies of Li ion cathode materials and other important transition metal oxides systems that involve complex electrochemical and catalytic reactions.

Effect of axial magnetic field on a 2.45 GHz permanent magnet ECR ion source.

PubMed

Nakamura, T; Wada, H; Asaji, T; Furuse, M

2016-02-01

Herein, we conduct a fundamental study to improve the generation efficiency of a multi-charged ion source using argon. A magnetic field of our electron cyclotron resonance ion source is composed of a permanent magnet and a solenoid coil. Thereby, the axial magnetic field in the chamber can be tuned. Using the solenoid coil, we varied the magnetic field strength in the plasma chamber and measured the ion beam current extracted at the electrode. We observed an approximately three times increase in the Ar(4+) ion beam current when the magnetic field on the extractor-electrode side of the chamber was weakened. From our results, we can confirm that the multi-charged ion beam current changes depending on magnetic field intensity in the plasma chamber.

Study on radiation production in the charge stripping section of the RISP linear accelerator

NASA Astrophysics Data System (ADS)

Oh, Joo-Hee; Oranj, Leila Mokhtari; Lee, Hee-Seock; Ko, Seung-Kook

2015-02-01

The linear accelerator of the Rare Isotope Science Project (RISP) accelerates 200 MeV/nucleon 238U ions in a multi-charge states. Many kinds of radiations are generated while the primary beam is transported along the beam line. The stripping process using thin carbon foil leads to complicated radiation environments at the 90-degree bending section. The charge distribution of 238U ions after the carbon charge stripper was calculated by using the LISE++ program. The estimates of the radiation environments were carried out by using the well-proved Monte Carlo codes PHITS and FLUKA. The tracks of 238U ions in various charge states were identified using the magnetic field subroutine of the PHITS code. The dose distribution caused by U beam losses for those tracks was obtained over the accelerator tunnel. A modified calculation was applied for tracking the multi-charged U beams because the fundamental idea of PHITS and FLUKA was to transport fully-ionized ion beam. In this study, the beam loss pattern after a stripping section was observed, and the radiation production by heavy ions was studied. Finally, the performance of the PHITS and the FLUKA codes was validated for estimating the radiation production at the stripping section by applying a modified method.

Photoionization and Photofragmentation of Carbon Fullerene Molecular Ions

NASA Astrophysics Data System (ADS)

Baral, Kiran Kumar

Cross sections are reported for single and double photoionization accompanied by the loss of as many as seven pairs of C atoms of C60 + and C70+ fullerene molecular ions in the photon energy range 18 eV to 150 eV. These measurements were performed at the Advanced Light Source (ALS) by merging a mass-selected ion beam with a beam of monochromatized synchrotron radiation. Threshold energies were determined for the formation of doubly and triply charged fragment ions from parent ions C60+ and C70+. The energy dependences of cross-sections for direct photoionization yielding C60 2+ and C702+ are compared with those for forming different doubly and triply charged fullerene fragment ions. Two-dimensional product ion scans were measured and quantified at four discrete photon energies: 35 eV, 65 eV, 105 eV and 140 eV, in the vacuum ultraviolet region, providing a comprehensive mapping of the product channels involving single ionization of fullerene ions C60+ and C 70+ accompanied by fragmentation. Since fullerenes are composed of even numbers of carbon atoms, the fragmentation occurs by the loss of differing numbers of carbon atom pairs. In addition to pure ionization, fragmentation product channels become relatively more important at higher photon energies.

Expanded Definition of the Oxidation State

ERIC Educational Resources Information Center

Loock, Hans-Peter

2011-01-01

A proposal to define the oxidation state of an atom in a compound as the hypothetical charge of the corresponding atomic ion that is obtained by heterolytically cleaving its bonds such that the atom with the higher electronegativity in a bond is allocated all electrons in the bond. Bonds between like atoms are cleaved homolytically. This…

Multi-purpose two- and three-dimensional momentum imaging of charged particles for attosecond experiments at 1 kHz repetition rate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Månsson, Erik P., E-mail: erik.mansson@sljus.lu.se; Sorensen, Stacey L.; Gisselbrecht, Mathieu

2014-12-15

We report on the versatile design and operation of a two-sided spectrometer for the imaging of charged-particle momenta in two dimensions (2D) and three dimensions (3D). The benefits of 3D detection are to discern particles of different mass and to study correlations between fragments from multi-ionization processes, while 2D detectors are more efficient for single-ionization applications. Combining these detector types in one instrument allows us to detect positive and negative particles simultaneously and to reduce acquisition times by using the 2D detector at a higher ionization rate when the third dimension is not required. The combined access to electronic andmore » nuclear dynamics available when both sides are used together is important for studying photoreactions in samples of increasing complexity. The possibilities and limitations of 3D momentum imaging of electrons or ions in the same spectrometer geometry are investigated analytically and three different modes of operation demonstrated experimentally, with infrared or extreme ultraviolet light and an atomic/molecular beam.« less

Metastable Atom-Activated Dissociation Mass Spectrometry of Phosphorylated and Sulfonated Peptides in Negative Ion Mode

NASA Astrophysics Data System (ADS)

Cook, Shannon L.; Jackson, Glen P.

2011-06-01

The dissociation behavior of phosphorylated and sulfonated peptide anions was explored using metastable atom-activated dissociation mass spectrometry (MAD-MS) and collision-induced dissociation (CID). A beam of high kinetic energy helium (He) metastable atoms was exposed to isolated phosphorylated and sulfonated peptides in the 3- and 2- charge states. Unlike CID, where phosphate losses are dominant, the major dissociation channels observed using MAD were Cα - C peptide backbone cleavages and neutral losses of CO2, H2O, and [CO2 + H2O] from the charge reduced (oxidized) product ion, consistent with an electron detachment dissociation (EDD) mechanism such as Penning ionization. Regardless of charge state or modification, MAD provides ample backbone cleavages with little modification loss, which allows for unambiguous PTM site determination. The relative abundance of certain fragment ions in MAD is also demonstrated to be somewhat sensitive to the number and location of deprotonation sites, with backbone cleavage somewhat favored adjacent to deprotonated sites like aspartic acid residues. MAD provides a complementary dissociation technique to CID, ECD, ETD, and EDD for peptide sequencing and modification identification. MAD offers the unique ability to analyze highly acidic peptides that contain few to no basic amino acids in either negative or positive ion mode.

Secondary ion emission from Ti, V, Cu, Ag and Au surfaces under KeV Cs + irradiation

NASA Astrophysics Data System (ADS)

van der Heide, P. A. W.

2005-02-01

Low energy mono-atomic singly charged secondary ion emissions from Ti, V, Cu, Ag and Au substrates during the initial stages of sputtering with Cs + primary ions have been studied. With the exception of the Ag - secondary ions, all exhibited exponential like correlations with the Cs induced work function changes. This, along with the lack of variations in the valence band structure around the Fermi edge, is consistent with resonance charge transfer to/from states located at the Fermi edge. The insensitivity of Ag - to work function appears to stem from the dominance of a separate ion formation process, namely charge transfer into vacant 4d states in the sputtered population, which themselves appear to be produced through collective oscillations. A similar excitation-mediated process involving different levels also appears to be active in the formation of other negatively charged transition metal ions, albeit to a much lesser degree.

Mean excitation energies for molecular ions

NASA Astrophysics Data System (ADS)

Jensen, Phillip W. K.; Sauer, Stephan P. A.; Oddershede, Jens; Sabin, John R.

2017-03-01

The essential material constant that determines the bulk of the stopping power of high energy projectiles, the mean excitation energy, is calculated for a range of smaller molecular ions using the RPA method. It is demonstrated that the mean excitation energy of both molecules and atoms increase with ionic charge. However, while the mean excitation energies of atoms also increase with atomic number, the opposite is the case for mean excitation energies for molecules and molecular ions. The origin of these effects is explained by considering the spectral representation of the excited state contributing to the mean excitation energy.

HEAVY ION LINEAR ACCELERATOR

DOEpatents

Van Atta, C.M.; Beringer, R.; Smith, L.

1959-01-01

A linear accelerator of heavy ions is described. The basic contributions of the invention consist of a method and apparatus for obtaining high energy particles of an element with an increased charge-to-mass ratio. The method comprises the steps of ionizing the atoms of an element, accelerating the resultant ions to an energy substantially equal to one Mev per nucleon, stripping orbital electrons from the accelerated ions by passing the ions through a curtain of elemental vapor disposed transversely of the path of the ions to provide a second charge-to-mass ratio, and finally accelerating the resultant stripped ions to a final energy of at least ten Mev per nucleon.

Spectroscopy of Highly Charged Tin Ions for AN Extreme Ultraviolet Light Source for Lithography

NASA Astrophysics Data System (ADS)

Torretti, Francesco; Windberger, Alexander; Ubachs, Wim; Hoekstra, Ronnie; Versolato, Oscar; Ryabtsev, Alexander; Borschevsky, Anastasia; Berengut, Julian; Crespo Lopez-Urrutia, Jose

2017-06-01

Laser-produced tin plasmas are the prime candidates for the generation of extreme ultraviolet (EUV) light around 13.5 nm in nanolithographic applications. This light is generated primarily by atomic transitions in highly charged tin ions: Sn^{8+}-Sn^{14+}. Due to the electronic configurations of these charge states, thousands of atomic lines emit around 13.5 nm, clustered in a so-called unresolved transition array. As a result, accurate line identification becomes difficult in this regime. Nevertheless, this issue can be circumvented if one turns to the optical: with far fewer atomic states, only tens of transitions take place and the spectra can be resolved with far more ease. We have investigated optical emission lines in an electron-beam-ion-trap (EBIT), where we managed to charge-state resolve the spectra. Based on this technique and on a number of different ab initio techniques for calculating the level structure, the optical spectra could be assigned [1,2]. As a conclusion the assignments of EUV transitions in the literature require corrections. The EUV and optical spectra are measured simultaneously in the controlled conditions of the EBIT as well as in a droplet-based laser-produced plasma source providing information on the contribution of Sn^{q+} charge states to the EUV emission. [1] A. Windberger, F. Torretti, A. Borschevsky, A. Ryabtsev, S. Dobrodey, H. Bekker, E. Eliav, U. Kaldor, W. Ubachs, R. Hoekstra, J.R. Crespo Lopez-Urrutia, O.O. Versolato, Analysis of the fine structure of Sn^{11+} - Sn^{14+} ions by optical spectroscopy in an electron beam ion trap, Phys. Rev. A 94, 012506 (2016). [2] F. Torretti, A. Windberger, A. Ryabtsev, S. Dobrodey, H. Bekker, W. Ubachs, R. Hoekstra, E.V. Kahl, J.C. Berengut, J.R. Crespo Lopez-Urrutia, O.O. Versolato, Optical spectroscopy of complex open 4d-shell ions Sn^{7+} - Sn^{10+}, arXiv:1612.00747

Observation of the continuous stern-gerlach effect on an electron bound in an atomic Ion

PubMed

Hermanspahn; Haffner; Kluge; Quint; Stahl; Verdu; Werth

2000-01-17

We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus.

Atomic Data for Nebular Abundance Determinations: Photoionization and Recombination Properties of Xenon Ions

NASA Astrophysics Data System (ADS)

Sterling, Nicholas C.; Kerlin, Austin B.

2016-01-01

We present preliminary results of a study of the photoionization (PI) and recombination properties of low-charge Xe ions. The abundances of neutron(n)-capture elements (atomic number Z > 30) are of interest in planetary nebulae (PNe) since they can be enriched by slow n-capture nucleosynthesis (the ``s-process'') in the progenitor asymptotic giant branch (AGB) stars. Xe is particularly valuable, because it is the most widely-observed ``heavy-s'' species (Z > 40) in PNe. Its abundance relative to lighter n-capture elements can be used to determine s-process neutron exposures, and constrain s-process enrichment patterns as a function of progenitor metallicity. Using the atomic structure code AUTOSTRUCTURE (Badnell 2011, Comp. Phys. Comm., 182, 1528), we have computed multi-configuration Breit-Pauli distorted-wave PI cross sections and radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for neutral through six-times ionized Xe, data which are critically needed for accurate Xe abundance determinations in ionized nebulae. We find good agreement between our computed direct PI cross sections and experimental measurements. Internal uncertainties are estimated for our calculations by using three different configuration interaction expansions for each ion, and by testing the sensitivity of our results to the radial orbital scaling parameters. As found for other n-capture elements (Sterling & Witthoeft 2011, A&A, 529, A147; Sterling 2011, A&A, 533, A62), DR is the dominant recombination mechanism for Xe ions at nebular temperatures (~104 K). Following Sterling et al. (2015, ApJS, 218, 25), these data will be added to nebular modeling codes to compute ionization correction factors for unobserved Xe ions in PNe, which will enable elemental Xe abundances to be determined with much higher accuracy than is currently possible. This work is supported by NSF award AST-1412928.

Characterization of xenon ion and neutral interactions in a well-characterized experiment

NASA Astrophysics Data System (ADS)

Patino, Marlene I.; Wirz, Richard E.

2018-06-01

Interactions between fast ions and slow neutral atoms are commonly dominated by charge-exchange and momentum-exchange collisions, which are important to understanding and simulating the performance and behavior of many plasma devices. To investigate these interactions, this work developed a simple, well-characterized experiment that accurately measures the behavior of high energy xenon ions incident on a background of xenon neutral atoms. By using well-defined operating conditions and a simple geometry, these results serve as canonical data for the development and validation of plasma models and models of neutral beam sources that need to ensure accurate treatment of angular scattering distributions of charge-exchange and momentum-exchange ions and neutrals. The energies used in this study are relevant for electric propulsion devices ˜1.5 keV and can be used to improve models of ion-neutral interactions in the plume. By comparing these results to both analytical and computational models of ion-neutral interactions, we discovered the importance of (1) accurately treating the differential cross-sections for momentum-exchange and charge-exchange collisions over a large range of neutral background pressures and (2) properly considering commonly overlooked interactions, such as ion-induced electron emission from nearby surfaces and neutral-neutral ionization collisions.

Laser-driven atomic-probe-beam diagnostics

NASA Astrophysics Data System (ADS)

Knyazev, B. A.; Greenly, J. B.; Hammer, D. A.

2000-12-01

A new laser-driven atomic-probe-beam diagnostic (LAD) is proposed for local, time-resolved measurements of electric field and ion dynamics in the accelerating gap of intense ion beam diodes. LAD adds new features to previous Stark-shift diagnostics which have been progressively developed in several laboratories, from passive observation of Stark effect on ion species or fast (charge-exchanged) neutrals present naturally in diodes, to active Stark atomic spectroscopy (ASAS) in which selected probe atoms were injected into the gap and excited to suitable states by resonant laser radiation. The LAD scheme is a further enhancement of ASAS in which the probe atoms are also used as a local (laser-ionized) ion source at an instant of time. Analysis of the ion energy and angular distribution after leaving the gap enables measurement, at the chosen ionization location in the gap, of both electrostatic potential and the development of ion divergence. Calculations show that all of these quantities can be measured with sub-mm and ns resolution. Using lithium or sodium probe atoms, fields from 0.1 to 10 MV/cm can be measured.

Coexisting stable conformations of gaseous protein ions.

PubMed Central

Suckau, D; Shi, Y; Beu, S C; Senko, M W; Quinn, J P; Wampler, F M; McLafferty, F W

1993-01-01

For further insight into the role of solvent in protein conformer stabilization, the structural and dynamic properties of protein ions in vacuo have been probed by hydrogen-deuterium exchange in a Fourier-transform mass spectrometer. Multiply charged ions generated by electrospray ionization of five proteins show exchange reactions with 2H2O at 10(-7) torr (1 torr = 133.3 Pa) exhibiting pseudo-first-order kinetics. Gas-phase compactness of the S-S cross-linked RNase A relative to denatured S-derivatized RNase A is indicated by exchange of 35 and 135 hydrogen atoms, respectively. For pure cytochrome c ions, the existence of at least three distinct gaseous conformers is indicated by the substantially different values--52, 113, and 74--of reactive H atoms; the observation of these same values for ions of a number--2, 7, and 5, respectively--of different charge states indicates conformational insensitivity to coulombic forces. For each of these conformers, the compactness in vacuo indicated by these values corresponds directly to that of a known conformer structure in the solution from which the conformer ions are produced by electrospray. S-derivatized RNase A ions also exist as at least two gaseous conformers exchanging 50-140 H atoms. Gaseous conformer ions are isometrically stable for hours; removal of solvent greatly increases conformational rigidity. More specific ion-molecule reactions could provide further details of conformer structures. Images PMID:8381533

Semiannual and solar activity variations of daytime plasma observed by DEMETER in the ionosphere-plasmasphere transition region

NASA Astrophysics Data System (ADS)

Li, L. Y.; Cao, J. B.; Yang, J. Y.; Berthelier, J. J.; Lebreton, J.-P.

2015-12-01

Using the plasma data of Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite and the NRLMSISE-00 atmospheric model, we examined the semiannual and solar activity variations of the daytime plasma and neutral composition densities in the ionosphere-plasmasphere transition region (~670-710 km). The results demonstrate that the semiannually latitudinal variation of the daytime oxygen ions (O+) is basically controlled by that of neutral atomic oxygen (O), whereas the latitude distributions of the helium and hydrogen ions (He+ and H+) do not fully depend on the neutral atomic helium (He) and hydrogen (H). The summer enhancement of the heavy oxygen ions is consistent with the neutral O enhancement in the summer hemisphere, and the oxygen ion density has significantly the summer-dense and winter-tenuous hemispheric asymmetry with respect to the dip equator. Although the winter enhancements of the lighter He+ and H+ ions are also associated with the neutral He and H enhancements in the winter hemisphere, the high-density light ions (He+ and H+) and electrons (e-) mainly appear at the low and middle magnetic latitudes (|λ| < 50°). The equatorial accumulations of the light plasma species indicate that the light charged particles (He+, H+, and e-) are easily transported by some equatorward forces (e.g., the magnetic mirror force and centrifugal force). The frequent Coulomb collisions between the charged particles probably lead to the particle trappings at different latitudes. Moreover, the neutral composition densities also influence their ion concentrations during different solar activities. From the low-F10.7 year (2007-2008) to the high-F10.7 year (2004-2005), the daytime oxygen ions and electrons increase with the increasing neutral atomic oxygen, whereas the daytime hydrogen ions tend to decrease with the decreasing neutral atomic hydrogen. The helium ion density has no obvious solar activity variation, suggesting that the generation (via the neutral He photoionization) and loss (via the charge exchange with neutral nitrogen N2 and/or the recombination with electrons) of the daytime He+ ions are comparable during different solar activities.

Observation and modeling of interspecies ion separation in inertial confinement fusion implosions via imaging x-ray spectroscopy

DOE PAGES

Joshi, Tirtha Raj; Hakel, Peter; Hsu, Scott C.; ...

2017-03-22

In this article, we report the first direct experimental evidence of interspecies ion separation in direct-drive inertial confinement fusion experiments performed at the OMEGA laser facility via spectrally, temporally, and spatially resolved imaging x-ray-spectroscopy data [S. C. Hsu et al., Europhys. Lett. 115, 65001 (2016)]. These experiments were designed based on the expectation that interspecies ion thermo-diffusion would be the strongest for species with a large mass and charge difference. The targets were spherical plastic shells filled with D2 and a trace amount of Ar (0.1% or 1% by atom). Ar K-shell spectral features were observed primarily between the timemore » of first-shock convergence and slightly before the neutron bang time, using a time- and space-integrated spectrometer, a streaked crystal spectrometer, and two gated multi-monochromatic x-ray imagers fielded along quasi-orthogonal lines of sight. Detailed spectroscopic analyses of spatially resolved Ar K-shell lines reveal the deviation from the initial 1% Ar gas fill and show both Ar-concentration enhancement and depletion at different times and radial positions of the implosion. The experimental results are interpreted using radiation-hydrodynamic simulations that include recently implemented, first-principles models of interspecies ion diffusion. Lastly, the experimentally inferred Ar-atom fraction profiles agree reasonably with calculated profiles associated with the incoming and rebounding first shock.« less

Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

NASA Astrophysics Data System (ADS)

M, Chabot; K, Béroff; T, Pino; G, Féraud; N, Dothi; Padellec A, Le; G, Martinet; S, Bouneau; Y, Carpentier

2012-11-01

We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn-*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

The effects of vortex like distributed electron in magnetized multi-ion dusty plasmas

NASA Astrophysics Data System (ADS)

Haider, Md. Masum; Ferdous, Tahmina; Duha, Syed S.

2014-09-01

The nonlinear propagation of small but finite amplitude dust-ion-acoustic solitary waves in a magnetized, collisionless dusty plasma is investigated theoretically. It has been assumed that the electrons are trapped following the vortex-like distribution and that the negatively and positively charged ions are mobile with the presence of charge fluctuating stationary dusts, where ions mass provide the inertia and restoring forces are provided by the thermal pressure of hot electrons. A reductive perturbation method was employed to obtain a modified Korteweg-de Vries (mK-dV) equation for the first-order potential and a stationary solution is obtained. The effect of the presence of trapped electrons, negatively and positively charged ions and arbitrary charged dust grains are discussed.

Ionization based multi-directional flow sensor

DOEpatents

Chorpening, Benjamin T [Morgantown, WV; Casleton, Kent H [Morgantown, WV

2009-04-28

A method, system, and apparatus for conducting real-time monitoring of flow (airflow for example) in a system (a hybrid power generation system for example) is disclosed. The method, system and apparatus measure at least flow direction and velocity with minimal pressure drop and fast response. The apparatus comprises an ion source and a multi-directional collection device proximate the ion source. The ion source is configured to generate charged species (electrons and ions for example). The multi-directional collection source is configured to determine the direction and velocity of the flow in real-time.

H- and He-like Charge-Exchange Induced X-ray Emission due to Ion Collisions with H, He, and H2

NASA Astrophysics Data System (ADS)

Cumbee, Renata; Mullen, Patrick; Miller, Ansley; Lyons, David; Shelton, Robin L.; Schultz, David R.; Stancil, Phillip C.; Leutenegger, Maurice A.

2017-08-01

When a hot plasma collides with a cold neutral gas interactions occur between the microscopic constituents including charge exchange (CX). CX is a process in which an electron can be transferred from a neutral atom or molecule into an excited energy level of an ion. Following this transfer, the excited electron relaxes to lower energy levels, emitting X-rays. This process has been established as a primary source of X-ray emission within our solar system, such as when the solar wind interacts with cometary and planetary atmospheres, and outside of our solar system, such as in the hot outflows of starburst galaxies.Since the CX X-ray emission spectrum varies greatly with collision velocity, it is critical that realistic CX data are included in X-ray spectral models of astrophysical environments in which CX might be significant in order to correctly estimate the ion abundance and plasma velocities. Here, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for a variety of collision energies relevant to various astrophysical environments. Collisions of bare and H-like C, N, O, Ne, Mg, Al, Si, P, S, and Cl ions are shown with H, He, and H2 as the neutral collision targets. An X-ray model using line ratios for C-Si ions is then performed within XSPEC for a region of the Cygnus Loop supernova remnant for 8 collision energies in order to highlight the variation in CX spectral models with collision energy.R. Cumbee’s research was partially supported by an appointment to the NASA Postdoctoral Program at NASA GSFC, administered by Universities Space Research Association under contract with NASA. Work at UGA was partially supported by NASA grants NNX09AC46G and NNG09WF24I.

Surface structure modification of single crystal graphite after slow, highly charged ion irradiation

NASA Astrophysics Data System (ADS)

Alzaher, I.; Akcöltekin, S.; Ban-d'Etat, B.; Manil, B.; Dey, K. R.; Been, T.; Boduch, P.; Rothard, H.; Schleberger, M.; Lebius, H.

2018-04-01

Single crystal graphite was irradiated by slow, highly charged ions. The modification of the surface structure was studied by means of Low-Energy Electron Diffraction. The observed damage cross section increases with the potential energy, i.e. the charge state of the incident ion, at a constant kinetic energy. The potential energy is more efficient for the damage production than the kinetic energy by more than a factor of twenty. Comparison with earlier results hints to a strong link between early electron creation and later target atom rearrangement. With increasing ion fluence, the initially large-scale single crystal is first transformed into μ m-sized crystals, before complete amorphisation takes place.

Development of a collinear laser spectrometer facility at VECC: First test result

NASA Astrophysics Data System (ADS)

Ali, Md Sabir; Ray, Ayan; Raja, Waseem; Bandyopadhyay, Arup; Naik, Vaishali; Polley, Asish; Chakrabarti, Alok

2018-04-01

We report here the development of collinear laser spectroscopy (CLS) system at VECC for the study of hyperfine spectrum and isotopic shift of stable and unstable isotopes. The facility is first of its kind in the country allowing measurement of hyperfine splitting of atomic levels using atomic beams. The CLS system is installed downstream of the focal plane of the existing isotope separator online (ISOL) facility at VECC and is recently commissioned by successfully resolving the fluorescence spectrum of the hyperfine levels in ^{85,87}Rb. The atomic beams of Rb were produced by charge exchange of 8 keV Rb ion beam which were produced, extracted and transported to the charge exchange cell using the ion sources, extractor and the beam-line magnets of the ISOL facility. The laser propagating opposite to the ion / atom beam direction was allowed to interact with the atom beam and fluorescence spectrum was recorded. The experimental set-up and the experiment conducted are reported in detail. The measures needed to be carried out for improving the sensitivity to a level necessary for studying short-lived exotic nuclei have also been discussed.

Recent Progress in the Development of a Multi-Layer Green's Function Code for Ion Beam Transport

NASA Technical Reports Server (NTRS)

Tweed, John; Walker, Steven A.; Wilson, John W.; Tripathi, Ram K.

2008-01-01

To meet the challenge of future deep space programs, an accurate and efficient engineering code for analyzing the shielding requirements against high-energy galactic heavy radiation is needed. To address this need, a new Green's function code capable of simulating high charge and energy ions with either laboratory or space boundary conditions is currently under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of the Neumann-asymptotic expansions with non-perturbative corrections. The code contains energy loss due to straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts. Previous reports show that the new code accurately models the transport of ion beams through a single slab of material. Current research efforts are focused on enabling the code to handle multiple layers of material and the present paper reports on progress made towards that end.

Hydrodynamic model for expansion and collisional relaxation of x-ray laser-excited multi-component nanoplasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saxena, Vikrant, E-mail: vikrant.saxena@desy.de; Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg; Ziaja, Beata, E-mail: ziaja@mail.desy.de

The irradiation of an atomic cluster with a femtosecond x-ray free-electron laser pulse results in a nanoplasma formation. This typically occurs within a few hundred femtoseconds. By this time the x-ray pulse is over, and the direct photoinduced processes no longer contributing. All created electrons within the nanoplasma are thermalized. The nanoplasma thus formed is a mixture of atoms, electrons, and ions of various charges. While expanding, it is undergoing electron impact ionization and three-body recombination. Below we present a hydrodynamic model to describe the dynamics of such multi-component nanoplasmas. The model equations are derived by taking the moments ofmore » the corresponding Boltzmann kinetic equations. We include the equations obtained, together with the source terms due to electron impact ionization and three-body recombination, in our hydrodynamic solver. Model predictions for a test case, expanding spherical Ar nanoplasma, are obtained. With this model, we complete the two-step approach to simulate x-ray created nanoplasmas, enabling computationally efficient simulations of their picosecond dynamics. Moreover, the hydrodynamic framework including collisional processes can be easily extended for other source terms and then applied to follow relaxation of any finite non-isothermal multi-component nanoplasma with its components relaxed into local thermodynamic equilibrium.« less

Correlation, Breit and Quantum Electrodynamics effects on energy level and transition properties of W54+ ion

NASA Astrophysics Data System (ADS)

Ding, Xiaobin; Sun, Rui; Koike, Fumihiro; Kato, Daiji; Murakami, Izumi; Sakaue, Hiroyuki A.; Dong, Chenzhong

2017-03-01

The electron correlation effects and Breit interaction as well as Quantum Electro-Dynamics (QED) effects were expected to have important contribution to the energy level and transition properties of heavy highly charged ions. The ground states [Ne]3s23p63d2 and first excited states [Ne]3s23p53d3 of W54+ ion have been studied by using Multi-Configuration Dirac-Fock method with the implementation of Grasp2K package. A restricted active space method was employed to investigate the correlation contribution from different models. The Breit interaction and QED effects were taken into account in the relativistic configuration interaction calculation with the converged wavefunction. It is found that the correlation contribution from 3s and 3p orbital have important contribution to the energy level, transition wavelength and probability of the ground and the first excited state of W54+ ion. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

Investigation of plasma behavior during noble gas injection in the end-cell of GAMMA 10/PDX by using the multi-fluid code ‘LINDA’

NASA Astrophysics Data System (ADS)

Islam, M. S.; Nakashima, Y.; Hatayama, A.

2017-12-01

The linear divertor analysis with fluid model (LINDA) code has been developed in order to simulate plasma behavior in the end-cell of linear fusion device GAMMA 10/PDX. This paper presents the basic structure and simulated results of the LINDA code. The atomic processes of hydrogen and impurities have been included in the present model in order to investigate energy loss processes and mechanism of plasma detachment. A comparison among Ar, Kr and Xe shows that Xe is the most effective gas on the reduction of electron and ion temperature. Xe injection leads to strong reduction in the temperature of electron and ion. The energy loss terms for both the electron and the ion are enhanced significantly during Xe injection. It is shown that the major energy loss channels for ion and electron are charge-exchange loss and radiative power loss of the radiator gas, respectively. These outcomes indicate that Xe injection in the plasma edge region is effective for reducing plasma energy and generating detached plasma in linear device GAMMA 10/PDX.

The interactions of high-energy, highly-charged ions with fullerenes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, R.; Berry, H.G.; Cheng, S.

1996-03-01

In 1985, Robert Curl and Richard Smalley discovered a new form of carbon, the fullerene, C{sub 60}, which consists of 60 carbon atoms in a closed cage resembling a soccer ball. In 1990, Kritschmer et al. were able to make macroscopic quantities of fullerenes. This has generated intense activity to study the properties of fullerenes. One area of research involves collisions between fullerenes and atoms, ions or electrons. In this paper we describe experiments involving interactions between fullerenes and highly charged ions in which the center-of-mass energies exceed those used in other work by several orders of magnitude. The highmore » values of projectile velocity and charge state result in excitation and decay processes differing significantly from those seen in studies 3 at lower energies. Our results are discussed in terms of theoretical models analogous to those used in nuclear physics and this provides an interesting demonstration of the unity of physics.« less

Shock-wave structure in a partially ionized gas

NASA Technical Reports Server (NTRS)

Lu, C. S.; Huang, A. B.

1974-01-01

The structure of a steady plane shock in a partially ionized gas has been investigated using the Boltzmann equation with a kinetic model as the governing equation and the discrete ordinate method as a tool. The effects of the electric field induced by the charge separation on the shock structure have also been studied. Although the three species of an ionized gas travel with approximately the same macroscopic velocity, the individual distribution functions are found to be very different. In a strong shock the atom distribution function may have double peaks, while the ion distribution function has only one peak. Electrons are heated up much earlier than ions and atoms in a partially ionized gas. Because the interactions of electrons with atoms and with ions are different, the ion temperature can be different from the atom temperature.

Semi-empirical scaling for ion-atom single charge exchange cross sections in the intermediate velocity regime

NASA Astrophysics Data System (ADS)

Friedman, B.; DuCharme, G.

2017-06-01

We present a semi-empirical scaling law for non-resonant ion-atom single charge exchange cross sections for collisions with velocities from {10}7 {{t}}{{o}} {10}9 {cm} {{{s}}}-1 and ions with positive charge q< 8. Non-resonant cross sections tend to have a velocity peak at collision velocities v≲ 1 {{a}}{{u}} with exponential decay around this peak. We construct a scaling formula for the location of this peak then choose a functional form for the cross section curve and scale it. The velocity at which the cross section peaks, v m, is proportional to the energy defect of the collision, {{Δ }}E, which we predict with the decay approximation. The value of the cross section maximum is proportional to the charge state q, inversely proportional to the target ionization energy I T, and inversely proportional to v m. For the shape of the cross section curve, we use a function that decays exponentially asymptotically at high and low velocities. We scale this function with parameters {v}{{m}},{I}{{T}},{Z}{{T}},{and} {Z}{{P}}, where the {Z}{{T},{{P}}} are the target and projectile atomic numbers. For the more than 100 cross section curves that we use to find the scaling rules, the scaling law predicts cross sections within a little over a factor of 2 on average.

Internal Energy Distribution in Sympathetically Cooled Molecular Ions

NASA Astrophysics Data System (ADS)

Thompson, Robert I.; Fisher, Amy; Harmon, Thomas; Winslade, Clayton; Ahmadi, Nasser

2002-05-01

Over the past year a research program at the University of Calgary has begun looking at the distribution of energy in the internal degrees of freedom (vibrational and rotational) of trapped and sympathetically cooled molecular ions. Ion traps are capable of holding mixed samples of charged atoms and molecules simultaneously. Atomic ions in the trapped cloud can be laser cooled by traditional techniques. The molecular ions are not directly laser cooled, but all of the trapped particles are charged so they interact strongly through Coulomb forces. It has been experimentally demonstrated that the external or translational degrees of freedom of the non-laser-cooled species are significantly lowered through this interaction (e.g. [1]). However, there is little known about the energy distribution in the in the internal degrees of freedom. This poster will outline the results of our theoretical work, as well as the technical design, construction, and initial work in the laboratory. [1] T. Baba and I. Waki, Jpn. J. Appl. Phys. 35, L1134 (1996).

Detection systems for mass spectrometry imaging: a perspective on novel developments with a focus on active pixel detectors.

PubMed

Jungmann, Julia H; Heeren, Ron M A

2013-01-15

Instrumental developments for imaging and individual particle detection for biomolecular mass spectrometry (imaging) and fundamental atomic and molecular physics studies are reviewed. Ion-counting detectors, array detection systems and high mass detectors for mass spectrometry (imaging) are treated. State-of-the-art detection systems for multi-dimensional ion, electron and photon detection are highlighted. Their application and performance in three different imaging modes--integrated, selected and spectral image detection--are described. Electro-optical and microchannel-plate-based systems are contrasted. The analytical capabilities of solid-state pixel detectors--both charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS) chips--are introduced. The Medipix/Timepix detector family is described as an example of a CMOS hybrid active pixel sensor. Alternative imaging methods for particle detection and their potential for future applications are investigated. Copyright © 2012 John Wiley & Sons, Ltd.

Atom-Level Understanding of the Sodiation Process in Silicon Anode Material.

PubMed

Jung, Sung Chul; Jung, Dae Soo; Choi, Jang Wook; Han, Young-Kyu

2014-04-03

Despite the exceptionally large capacities in Li ion batteries, Si has been considered inappropriate for applications in Na ion batteries. We report an atomic-level study on the applicability of a Si anode in Na ion batteries using ab initio molecular dynamics simulations. While crystalline Si is not suitable for alloying with Na atoms, amorphous Si can accommodate 0.76 Na atoms per Si atom, corresponding to a specific capacity of 725 mA h g(-1). Bader charge analyses reveal that the sodiation of an amorphous Si electrode continues until before the local Na-rich clusters containing neutral Na atoms are formed. The amorphous Na0.76Si phase undergoes a volume expansion of 114% and shows a Na diffusivity of 7 × 10(-10) cm(2) s(-1) at room temperature. Overall, the amorphous Si phase turns out quite attractive in performance compared to other alloy-type anode materials. This work suggests that amorphous Si might be a competitive candidate for Na ion battery anodes.

A high flux source of swift oxygen atoms

NASA Technical Reports Server (NTRS)

Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

1987-01-01

A source of swift oxygen atoms is described which has several unique features. A high current ion beam is produced by a microwave discharge, accelerated to 10 keV and the mass selected by a modified Du Pont 21-110 mass spectrometer. The O(+) beam exciting the mass spectrometer is focused into a rectangular shape with an energy spread of less than 1 eV. The next section of the machine decelerates the ion beam into a counterpropagating electron beam in order to minimize space charge effects. After deceleration, the ion beam intersects at 90 deg, a neutral oxygen atom beam, which via resonant charge exchange produces a mixture of O(+) and O. Any remaining O(+) are swept out of the beam by an electric field and differentially pumped away while the desired O beam, collimated by slits, impinges on the target. In situ monitoring of the target surface is done by X-ray photoelectron or Auger spectroscopy. Faraday cups provide flux measurements in the ion sections while the neutral flux is determined by a special torsion balance or by a quadrupole mass spectrometer specially adapted for swift atoms. While the vacuum from the source through the mass spectrometer is maintained by diffusion pumps, the rest of the machine is UHV.

Single and multiple ionization of C60 fullerenes and collective effects in collisions with highly charged C, F, and Si ions with energy 3 MeV/u

NASA Astrophysics Data System (ADS)

Kelkar, A. H.; Kadhane, U.; Misra, D.; Gulyas, L.; Tribedi, L. C.

2010-10-01

We have measured absolute cross sections for single, double, triple, and quadruple ionization of C60 in collisions with 3 MeV/u C, F, and Si projectile ions at various projectile charge states. The experiment was performed using the recoil-ion time-of-flight technique. Projectile charge state dependence of the ionization yields was compared mainly with a model based on the giant dipole plasmon resonance (GDPR). In some cases, the continuum-distorted-wave-eikonal-initial-state (CDW-EIS) model which is normally applied for ion-atom collisions was also used as a reference. An excellent qualitative agreement between the experimental data for single and double ionization and the GDPR model predictions was found for all projectile charge states.

Attractive non-DLVO forces induced by adsorption of monovalent organic ions.

PubMed

Smith, Alexander M; Maroni, Plinio; Borkovec, Michal

2017-12-20

Direct force measurements between negatively charged colloidal particles were carried out using an atomic force microscope (AFM) in aqueous solutions containing monovalent organic cations, namely tetraphenylarsonium (Ph 4 As + ), 1-hexyl-3-methylimidazolium (HMIM + ), and 1-octyl-3-methylimidazolium (OMIM + ). These ions adsorb to the particle surface, and induce a charge reversal. The forces become attractive at the charge neutralization point, but they are stronger than van der Waals forces. This additional and unexpected attraction decays exponentially with a decay length of a few nanometers, and is strikingly similar to the one previously observed in the presence of multivalent ions. This attractive force probably originates from coupled spontaneous charge fluctuations on the respective surfaces as initially suggested by Kirkwood and Shumaker.

Formation of multiply charged ions from large molecules using massive-cluster impact.

PubMed

Mahoney, J F; Cornett, D S; Lee, T D

1994-05-01

Massive-cluster impact is demonstrated to be an effective ionization technique for the mass analysis of proteins as large as 17 kDa. The design of the cluster source permits coupling to both magnetic-sector and quadrupole mass spectrometers. Mass spectra are characterized by the almost total absence of chemical background and a predominance of multiply charged ions formed from 100% glycerol matrix. The number of charge states produced by the technique is observed to range from +3 to +9 for chicken egg lysozyme (14,310 Da). The lower m/z values provided by higher charge states increase the effective mass range of analyses performed with conventional ionization by fast-atom bombardment or liquid secondary ion mass spectrometry.

Enhanced laboratory sensitivity to variation of the fine-structure constant using highly charged ions.

PubMed

Berengut, J C; Dzuba, V A; Flambaum, V V

2010-09-17

We study atomic systems that are in the frequency range of optical atomic clocks and have enhanced sensitivity to potential time variation of the fine-structure constant α. The high sensitivity is due to coherent contributions from three factors: high nuclear charge Z, high ionization degree, and significant differences in the configuration composition of the states involved. Configuration crossing keeps the frequencies in the optical range despite the large ionization energies. We discuss a few promising examples that have the largest α sensitivities seen in atomic systems.

ION ROCKET ENGINE

DOEpatents

Ehlers, K.W.; Voelker, F. III

1961-12-19

A thrust generating engine utilizing cesium vapor as the propellant fuel is designed. The cesium is vaporized by heat and is passed through a heated porous tungsten electrode whereby each cesium atom is fonized. Upon emergfng from the tungsten electrode, the ions are accelerated rearwardly from the rocket through an electric field between the tungsten electrode and an adjacent accelerating electrode grid structure. To avoid creating a large negative charge on the space craft as a result of the expulsion of the positive ions, a source of electrons is disposed adjacent the ion stream to neutralize the cesium atoms following acceleration thereof. (AEC)

Characteristics of the optical radiation from Kaufman thrusters

NASA Technical Reports Server (NTRS)

Milder, N. L.; Sovey, J. S.

1971-01-01

The optical radiation from plasma discharges of electron-bombardment mercury-ion thrusters was investigated. Spectrographic measurements indicated that the discharge was composed primarily of mercury atoms and singly charged ions. Excitation spectra of doubly charged mercury ions was measured to obtain the fraction of such ions in the discharge. Accomplishments of spectroscopic measurements of a hollow cathode thruster included the identification of two diagnostic lines in the mercury spectrum and the interpretation of the spectral amplitudes in terms of a superposition of primary and Maxwellian electron distributions. Potential application of optical techniques to thruster control applications was also suggested by the measurements.

Application of pulsed multi-ion irradiations in radiation damage research: A stochastic cluster dynamics simulation study

NASA Astrophysics Data System (ADS)

Hoang, Tuan L.; Nazarov, Roman; Kang, Changwoo; Fan, Jiangyuan

2018-07-01

Under the multi-ion irradiation conditions present in accelerated material-testing facilities or fission/fusion nuclear reactors, the combined effects of atomic displacements with radiation products may induce complex synergies in the structural materials. However, limited access to multi-ion irradiation facilities and the lack of computational models capable of simulating the evolution of complex defects and their synergies make it difficult to understand the actual physical processes taking place in the materials under these extreme conditions. In this paper, we propose the application of pulsed single/dual-beam irradiation as replacements for the expensive steady triple-beam irradiation to study radiation damages in materials under multi-ion irradiation.

Meteoric Ions in Planetary Ionospheres

NASA Technical Reports Server (NTRS)

Pesnell, W. D.; Grebowsky, Joseph M.; Vondrak, Richard R. (Technical Monitor)

2001-01-01

Solar system debris, in the form of meteoroids, impacts every planet. The flux, relative composition and speed of the debris at each planet depends on the planet's size and location in the solar system. Ablation in the atmosphere evaporates the meteoric material and leaves behind metal atoms. During the ablation process metallic ions are formed by impact ionization. For small inner solar system planets, including Earth, this source of ionization is typically small compared to either photoionization or charge exchange with ambient molecular ions. For Earth, the atmosphere above the main deposition region absorbs the spectral lines capable of ionizing the major metallic atoms (Fe and Mg) so that charge exchange with ambient ions is the dominant source. Within the carbon dioxide atmosphere of Mars (and possibly Venus), photoionization is important in determining the ion density. For a heavy planet like Jupiter, far from the sun, impact ionization of ablated neutral atoms by impacts with molecules becomes a prominent source of ionization due to the gravitational acceleration to high incident speeds. We will describe the processes and location and extent of metal ion layers for Mars, Earth and Jupiter, concentrating on flagging the uncertainties in the models at the present time. This is an important problem, because low altitude ionosphere layers for the planets, particularly at night, probably consist predominantly of metallic ions. Comparisons with Earth will be used to illustrate the differing processes in the three planetary atmospheres.

The formation of excited atoms during charge exchange between hydrogen ions and alkali atoms. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Nieman, R. A.

1971-01-01

The charge exchange cross sections for protons and various alkali atoms are calculated using the classical approximation of Gryzinski. It is assumed that the hydrogen atoms resulting from charge exchange exist in all possible excited states. Charge transfer collisions between protons and potassium as well as protons and sodium atoms are studied. The energy range investigated is between 4 and 30 keV. The theoretical calculations of the capture cross section and the cross section for the creation of metastable 2S hydrogen are compared to experimental values. Good quantitative agreement is found for the capture cross section but only qualitative agreement for the metastable cross section. Analysis of the Lyman alpha window in molecular oxygen suggests that measured values of the metastable cross section may be in error. Thick alkali target data are also presented. This allows the determination of the total electron loss cross section. Finally, some work was done with H2(+).

Development of the negative ion beams relevant to ITER and JT-60SA at Japan Atomic Energy Agency.

PubMed

Hanada, M; Kojima, A; Tobari, H; Nishikiori, R; Hiratsuka, J; Kashiwagi, M; Umeda, N; Yoshida, M; Ichikawa, M; Watanabe, K; Yamano, Y; Grisham, L R

2016-02-01

In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification. As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications.

Low-energy charge transfer for collisions of Si3+ with atomic hydrogen

NASA Astrophysics Data System (ADS)

Bruhns, H.; Kreckel, H.; Savin, D. W.; Seely, D. G.; Havener, C. C.

2008-06-01

Cross sections of charge transfer for Si3+ ions with atomic hydrogen at collision energies of ≈40-2500eV/u were carried out using a merged-beam technique at the Multicharged Ion Research Facility at Oak Ridge National Laboratory. The data span an energy range in which both molecular orbital close coupling (MOCC) and classical trajectory Monte Carlo (CTMC) calculations are available. The influence of quantum mechanical effects of the ionic core as predicted by MOCC is clearly seen in our results. However, discrepancies between our experiment and MOCC results toward higher collision energies are observed. At energies above 1000 eV/u good agreement is found with CTMC results.

Selected highly charged ions as prospective candidates for optical clocks with quality factors larger than 1015

NASA Astrophysics Data System (ADS)

Yu, Yan-mei; Sahoo, B. K.

2018-04-01

The Ni12 +, Cu13 +, Pd12 +, and Ag13 + highly charged ions (HCIs) are proposed for making very accurate optical clocks with the fractional uncertainties below 10-19 level. These HCIs have simple atomic energy levels, clock transitions with quality factors larger than 1015, and optical magnetic-dipole (M 1 ) transitions that can be used for laser cooling and detecting quantum jumps on the clock transitions by the shelving method. To demonstrate the projected fractional uncertainties, we estimate orders of magnitude of the Zeeman, Stark, blackbody radiation, and electric quadrupole shifts of the clock transitions by performing calculations of the relevant atomic properties in the above HCIs.

Charge exchange of highly charged argon ions as a function of projectile energy

NASA Astrophysics Data System (ADS)

Allen, F. I.; Biedermann, C.; Radtke, R.; Fussmann, G.

2007-03-01

X-ray emission of highly charged argon ions following charge exchange collisions with argon atoms has been measured as a function of projectile energy. The ions are extracted from the Electron Beam Ion Trap (EBIT) in Berlin and selected according to their massto-charge ratios. Experiments focussed on hydrogen-like and bare argon ions which were decelerated from 125q eV/amu to below 0.25q eV/amu prior to interaction with an argon gas target. The x-ray spectra recorded probe the cascading transitions resulting from electron capture into Rydberg states and are found to vary significantly with collision velocity. This indicates a shift in the orbital angular momentum of the capture state. Hardness ratios are observed to increase with decreasing projectile energy though at a rate which differs from the results of simulations. For comparison, measurements of the x-ray emission following charge exchange within the trap were carried out and are in agreement with the findings of the EBIT group at LLNL. Both of these in situ measurements, however, are in discrepancy with the results of the experiments using extracted ions.

Deep-down ionization of protoplanetary discs

NASA Astrophysics Data System (ADS)

Glassgold, A. E.; Lizano, S.; Galli, D.

2017-12-01

The possible occurrence of dead zones in protoplanetary discs subject to the magneto-rotational instability highlights the importance of disc ionization. We present a closed-form theory for the deep-down ionization by X-rays at depths below the disc surface dominated by far-ultraviolet radiation. Simple analytic solutions are given for the major ion classes, electrons, atomic ions, molecular ions and negatively charged grains. In addition to the formation of molecular ions by X-ray ionization of H2 and their destruction by dissociative recombination, several key processes that operate in this region are included, e.g. charge exchange of molecular ions and neutral atoms and destruction of ions by grains. Over much of the inner disc, the vertical decrease in ionization with depth into the disc is described by simple power laws, which can easily be included in more detailed modelling of magnetized discs. The new ionization theory is used to illustrate the non-ideal magnetohydrodynamic effects of Ohmic, Hall and Ambipolar diffusion for a magnetic model of a T Tauri star disc using the appropriate Elsasser numbers.

Electron removal from H and He atoms in collisions with C q+ , O q+ ions

NASA Astrophysics Data System (ADS)

Janev, R. K.; McDowell, M. R. C.

1984-06-01

Cross sections for electron capture and ionisation in collision of partially and completely stripped C q+ , N q+ and O q+ ions with hydrogen and helium atoms have been calculated at selected energies. The classical trajectory Monte Carlo method was used with a variable-charge pseudopotential to describe the interaction of the active electron with the projectile ion. A scalling relationship has been derived for the electron removal (capture and ionisation) cross section which allows a unifield representation of the data.

Measurement of visible and UV emission from Energetic Neutral Atom Precipitation (ENAP), on Spacelab

NASA Technical Reports Server (NTRS)

Tinsley, B. A.

1980-01-01

The charge exchange of plasmaspheric ions and exospheric H and O and of solar wind ions with exospheric and interplanetary H are sources of precipitating neutrals whose faint emission may be observed by the imaging spectrometric observatory during dark periods of the SL-1 orbit. Measurements of the interactions of these precipitating atoms with the thermosphere are needed to evaluate the heating and ionization effects on the atmosphere as well as the selective loss of i energetic ions from the sources (predominantly the ring current).

A model Ni-Al-Mo superalloy studied by ultraviolet pulsed-laser-assisted local-electrode atom-probe tomography.

PubMed

Tu, Yiyou; Plotnikov, Elizaveta Y; Seidman, David N

2015-04-01

This study investigates the effects of the charge-state ratio of evaporated ions on the accuracy of local-electrode atom-probe (LEAP) tomographic compositional and structural analyses, which employs a picosecond ultraviolet pulsed laser. Experimental results demonstrate that the charge-state ratio is a better indicator of the best atom-probe tomography (APT) experimental conditions compared with laser pulse energy. The thermal tails in the mass spectra decrease significantly, and the mass resolving power (m/Δm) increases by 87.5 and 185.7% at full-width half-maximum and full-width tenth-maximum, respectively, as the laser pulse energy is increased from 5 to 30 pJ/pulse. The measured composition of this alloy depends on the charge-state ratio of the evaporated ions, and the most accurate composition is obtained when Ni2+/Ni+ is in the range of 0.3-20. The γ(f.c.c.)/γ'(L12) interface is quantitatively more diffuse when determined from the measured concentration profiles for higher laser pulse energies. Conclusions of the APT compositional and structural analyses utilizing the same suitable charge-state ratio are more comparable than those collected with the same laser pulse energy.

Observation of interspecies ion separation in inertial-confinement-fusion implosions

DOE PAGES

Hsu, Scott C.; Joshi, Tirtha Raj; Hakel, Peter; ...

2016-10-24

Here we report direct experimental evidence of interspecies ion separation in direct-drive, inertial-confinement-fusion experiments on the OMEGA laser facility. These experiments, which used plastic capsules with D 2/Ar gas fill (1% Ar by atom), were designed specifically to reveal interspecies ion separation by exploiting the predicted, strong ion thermo-diffusion between ion species of large mass and charge difference. Via detailed analyses of imaging x-ray-spectroscopy data, we extract Ar-atom-fraction radial profiles at different times, and observe both enhancement and depletion compared to the initial 1%-Ar gas fill. The experimental results are interpreted with radiation-hydrodynamic simulations that include recently implemented, first-principles modelsmore » of interspecies ion diffusion. Finally, the experimentally inferred Ar-atom-fraction profiles agree reasonably, but not exactly, with calculated profiles associated with the incoming and rebounding first shock.« less

Mixing of the Interstellar and Solar Plasmas at the Heliospheric Interface

DOE PAGES

Pogorelov, N. V.; Borovikov, S. N.

2015-10-12

From the ideal MHD perspective, the heliopause is a tangential discontinuity that separates the solar wind plasma from the local interstellar medium plasma. There are physical processes, however, that make the heliopause permeable. They can be subdivided into kinetic and MHD categories. Kinetic processes occur on small length and time scales, and cannot be resolved with MHD equations. On the other hand, MHD instabilities of the heliopause have much larger scales and can be easily observed by spacecraft. The heliopause may also be a subject of magnetic reconnection. In this paper, we discuss mechanisms of plasma mixing at the heliopausemore » in the context of Voyager 1 observations. Numerical results are obtained with a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), which is a package of numerical codes capable of performing adaptive mesh refinement simulations of complex plasma flows in the presence of discontinuities and charge exchange between ions and neutral atoms. The flow of the ionized component is described with the ideal MHD equations, while the transport of atoms is governed either by the Boltzmann equation or multiple Euler gas dynamics equations. The code can also treat nonthermal ions and turbulence produced by them.« less

Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes

DOE PAGES

Wang, Bo; Li, Shaohong L.; Truhlar, Donald G.

2014-10-30

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Badermore » charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. Here, we conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.« less

Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes.

PubMed

Wang, Bo; Li, Shaohong L; Truhlar, Donald G

2014-12-09

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Bader charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. We conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.

Charge Transfer Reactions

NASA Astrophysics Data System (ADS)

Dennerl, Konrad

2010-12-01

Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

Formation of hollow atoms above a surface

NASA Astrophysics Data System (ADS)

Briand, Jean Pierre; Phaneuf, Ronald; Terracol, Stephane; Xie, Zuqi

2012-06-01

Slow highly stripped ions approaching or penetrating surfaces are known to capture electrons into outer shells of the ions, leaving the innermost shells empty, and forming hollow atoms. Electron capture occurs above and below the surfaces. The existence of hollow atoms below surfaces e.g. Ar atoms whose K and L shells are empty, with all electrons lying in the M and N shells, was demonstrated in 1990 [1]. At nm above surfaces, the excited ions may not have enough time to decay before hitting the surfaces, and the formation of hollow atoms above surfaces has even been questioned [2]. To observe it, one must increase the time above the surface by decelerating the ions. We have for the first time decelerated O^7+ ions to energies as low as 1 eV/q, below the minimum energy gained by the ions due to the acceleration by their image charge. As expected, no ion backscattering (trampoline effect) above dielectric (Ge) was observed and at the lowest ion kinetic energies, most of the observed x-rays were found to be emitted by the ions after surface contact. [4pt] [1] J. P. Briand et al., Phys.Rev.Lett. 65(1990)159.[0pt] [2] J.P. Briand, AIP Conference Proceedings 215 (1990) 513.

Charge Exchange: Velocity Dependent X-ray Emission Modeling

NASA Astrophysics Data System (ADS)

Cumbee, Renata

2017-06-01

Atomic collisions play a fundamental role in astrophysics, plasma physics, and fusion physics. Here, we focus on charge exchange (CX) between hot ions and neutral atoms and molecules. Even though charge exchange calculations can provide vital information, including neutral and ion density distributions, ion temperatures, elemental abundances, and ion charge state distributions in the environments considered, both theoretical calculations and laboratory studies of these processes lack the necessary reliability and/or coverage. In order to better understand the spectra we observe in astrophysical environments in which both hot plasma and neutral gas are present, including comets, the heliosphere, supernova remnants, galaxy clusters, star forming galaxies, the outflows of starburst galaxies, and cooling flows of hot gas in the intracluster medium, a thorough CX X-ray model is needed. Included in this model should be a complete set of X-ray line ratios for relevant ion and neutral interactions for a range of energies.In this work, theoretical charge exchange emission spectra are produced using cross sections calculated with widely applied approaches including the quantum mechanical molecular orbital close coupling (QMOCC), atomic orbital close coupling (AOCC), classical trajectory Monte Carlo (CTMC), and the multichannel Landau-Zener (MCLZ) methods. When possible, theoretical data are benchmarked to experiments. Using a comprehensive, but still far from complete, CX database, new models are performed for a variety of X-ray emitting environments. In an attempt to describe the excess emission in X-rays of the starburst galaxy M82, Ne X CX line ratios are compared to line ratios observed in the region. A more complete XSPEC X-ray emission model is produced for H-like and He-like C-Al ions colliding with H and He for a range of energies; 200 to 5000 eV/u. This model is applied to the northeast rim of the Cygnus Loop supernova remnant in an attempt to determine the contribution of CX within that region.This work was partially supported by NASA grants NNX09AC46G and NNG09WF24I and accomplished with the help of many collaborators including Phillip C. Stancil, David Lyons, Patrick Mullen, and Robin L. Shelton.

Recent trends in precision measurements of atomic and nuclear properties with lasers and ion traps

NASA Astrophysics Data System (ADS)

Block, Michael

2017-11-01

The X. international workshop on "Application of Lasers and Storage Devices in Atomic Nuclei Research" took place in Poznan in May 2016. It addressed the latest experimental and theoretical achievements in laser and ion trap-based investigations of radionuclides, highly charged ions and antiprotons. The precise determination of atomic and nuclear properties provides a stringent benchmark for theoretical models and eventually leads to a better understanding of the underlying fundamental interactions and symmetries. This article addresses some general trends in this field and highlights select recent achievements presented at the workshop. Many of these are covered in more detail within the individual contributions to this special issue of Hyperfine Interactions.

The effect of various quantum mechanically derived partial atomic charges on the bulk properties of chloride-based ionic liquids

NASA Astrophysics Data System (ADS)

Zolghadr, Amin Reza; Ghatee, Mohammad Hadi; Moosavi, Fatemeh

2016-08-01

Partial atomic charges using various quantum mechanical calculations for [Cnmim]Cl (n = 1, 4) ionic liquids (ILs) are obtained and used for development of molecular dynamics simulation (MD) force fields. The isolated ion pairs are optimized using HF, B3LYP, and MP2 methods for electronic structure with 6-311++G(d,p) basis set. Partial atomic charges are assigned to the atomic center with CHELPG and NBO methods. The effect of these sets of partial charges on the static and dynamic properties of ILs is evaluated by performing a series of MD simulations and comparing the essential thermodynamic properties with the available experimental data and available molecular dynamics simulation results. In contrast to the general trends reported for ionic liquids with BF4, PF6, and iodide anions (in which restrained electrostatic potential (RESP) charges are preferred), partial charges derived by B3LYP-NBO method are relatively good in prediction of the structural, dynamical, and thermodynamic energetic properties of the chloride based ILs.

Fast calculator for X-ray emission due to Radiative Recombination and Radiative Electron Capture in relativistic heavy-ion atom collisions

NASA Astrophysics Data System (ADS)

Herdrich, M. O.; Weber, G.; Gumberidze, A.; Wu, Z. W.; Stöhlker, Th.

2017-10-01

In experiments with highly charged, fast heavy ions the Radiative Recombination (RR) and Radiative Electron Capture (REC) processes have significant cross sections in an energy range of up to a few GeV / u . They are some of the most important charge changing processes in collisions of heavy ions with atoms and electrons, leading to the emission of a photon along with the formation of the ground and excited atomic states. Hence, for the understanding and planning of experiments, in particular for X-ray spectroscopy studies, at accelerator ring facilities, such as FAIR, it is crucial to have a good knowledge of these cross sections and the associated radiation characteristics. In the frame of this work a fast calculator, named RECAL, for the RR and REC process is presented and its capabilities are demonstrated with the analysis of a recently conducted experiment at the Experimental Storage Ring (ESR) at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany. A method is presented to determine unknown X-ray emission cross sections via normalization of the recorded spectra to REC cross sections calculated by RECAL.

The Response of the Ionospheric Cusp to the Solar Wind Through Two Perspectives: Low Energy Charged Particle In-Situ Measurements and Low-Energy Neutral Atom Imaging

NASA Technical Reports Server (NTRS)

Coffey, V. N.; Moore, T. E.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Rose, M. Franklin (Technical Monitor)

2000-01-01

The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission provides a new perspective on the study of the response of the magnetosphere/ionosphere system to changing solar wind conditions, particularly the variability of ion outflow. Learning to interpret this new type of data becomes an essential step in the process of melding these results with the wealth of in-situ charged particle observations obtained over the past 25 years. In order to understand how the in-situ data correspond to and contrast with IMAGE results we will perform a conjunctive study of event data from two instruments to shed light on the coupling of the solar wind and ionosphere from these different perspectives. We will use the Low Energy Neutral Atom instrument (LENA) which images energetic neutral atom emissions from upward flowing ionospheric ions and the Thermal Ion Dynamics Instrument (TIDE) on the Polar satellite which measures in-situ ion outflow from 0.3-300 eV. Our primary goal will be to understand how comparing the imaging and in-situ perspectives can aid in the analysis of both data sets.

Brownian Dynamics Simulations of Ion Transport through the VDAC

PubMed Central

Lee, Kyu Il; Rui, Huan; Pastor, Richard W.; Im, Wonpil

2011-01-01

It is important to gain a physical understanding of ion transport through the voltage-dependent anion channel (VDAC) because this channel provides primary permeation pathways for metabolites and electrolytes between the cytosol and mitochondria. We performed grand canonical Monte Carlo/Brownian dynamics (GCMC/BD) simulations to explore the ion transport properties of human VDAC isoform 1 (hVDAC1; PDB:2K4T) embedded in an implicit membrane. When the MD-derived, space-dependent diffusion constant was used in the GCMC/BD simulations, the current-voltage characteristics and ion number profiles inside the pore showed excellent agreement with those calculated from all-atom molecular-dynamics (MD) simulations, thereby validating the GCMC/BD approach. Of the 20 NMR models of hVDAC1 currently available, the third one (NMR03) best reproduces both experimental single-channel conductance and ion selectivity (i.e., the reversal potential). In addition, detailed analyses of the ion trajectories, one-dimensional multi-ion potential of mean force, and protein charge distribution reveal that electrostatic interactions play an important role in the channel structure and ion transport relationship. Finally, the GCMC/BD simulations of various mutants based on NMR03 show good agreement with experimental ion selectivity. The difference in ion selectivity between the wild-type and the mutants is the result of altered potential of mean force profiles that are dominated by the electrostatic interactions. PMID:21281575

Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.

PubMed

Luo, Kun; Roberts, Matthew R; Hao, Rong; Guerrini, Niccoló; Pickup, David M; Liu, Yi-Sheng; Edström, Kristina; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

2016-07-01

During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates.

Single and multiple ionization of C{sub 60} fullerenes and collective effects in collisions with highly charged C, F, and Si ions with energy 3 MeV/u

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelkar, A. H.; Kadhane, U.; Misra, D.

2010-10-15

We have measured absolute cross sections for single, double, triple, and quadruple ionization of C{sub 60} in collisions with 3 MeV/u C, F, and Si projectile ions at various projectile charge states. The experiment was performed using the recoil-ion time-of-flight technique. Projectile charge state dependence of the ionization yields was compared mainly with a model based on the giant dipole plasmon resonance (GDPR). In some cases, the continuum-distorted-wave-eikonal-initial-state (CDW-EIS) model which is normally applied for ion-atom collisions was also used as a reference. An excellent qualitative agreement between the experimental data for single and double ionization and the GDPR modelmore » predictions was found for all projectile charge states.« less

Ionization source utilizing a jet disturber in combination with an ion funnel and method of operation

DOEpatents

Smith, Richard D.; Kim, Taeman; Tang, Keqi; Udseth, Harold R.

2003-06-24

A jet disturber used in combination with an ion funnel to focus ions and other charged particles generated at or near atmospheric pressure into a relatively low pressure region, which allows increased conductance of the ions and other charged particles. The jet disturber is positioned within an ion funnel and may be interfaced with a multi-capillary inlet juxtaposed between an ion source and the interior of an instrument maintained at near atmospheric pressure. The invention finds particular advantages when deployed to improve the ion transmission between an electrospray ionization source and the first vacuum stage of a mass spectrometer.

Metallic ions in the equatorial ionosphere

NASA Technical Reports Server (NTRS)

Aikin, A. C.; Goldberg, R. A.

1972-01-01

Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.

State-selective charge exchange in slow collisions of Si3+ ions with H atoms: A molecular state close coupling treatment*)

NASA Astrophysics Data System (ADS)

Joseph, Dwayne C.; Saha, Bidhan C.

2012-11-01

Charge transfer cross sections are calculated by employing both the quantal and semiclassical ɛ(R) molecular orbital close coupling (MOCC) approximations in the adiabatic representation and compared with other theoretical and experimental results

X-ray And EUV Spectroscopy Of Highly Charged Tungsten Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biedermann, Christoph; Radtke, Rainer

2009-09-10

The Berlin EBIT has been established by the Max-Planck-Institut fuer Plasmaphysik to generate atomic physics data in support of research in the field of controlled nuclear fusion, by measuring the radiation from highly charged ions in the x-ray, extreme ultraviolet and visible spectral ranges and providing valuable diagnostics for high temperature plasmas. In future fusion devices, for example ITER, currently being constructed at Cadarache, France, the plasma facing components will be armored with high-Z materials, most likely tungsten, due to the favorable properties of this element. At the same time the tremendous radiation cooling of these high-Z materials represents amore » threat to fusion and obliges one to monitor carefully the radiation. With EBIT a selected ensemble of ions in specific charge states can be produced, stored and excited for spectroscopic investigations. Employing this technique, we have for example resolved the wide structure observed around 5 nm at the ASDEX Upgrade tokamak as originating from E1-transitions into the open 4d shell of tungsten ions in charge states 25+ to 37+ producing a band-like emission pattern. Further, these ions emit well-separated M1 lines in the EUV range around 65 nm suitable for plasma diagnostics. Kr-like to Cr-like tungsten ions (38+ to 50+) show strong soft-x-ray lines in the range 0.5 to 2 and 5 to 15 nm. Lines of even higher charged tungsten ions, up to Ne-like W{sup 64+}, abundant in the core plasma of present and future fusion test devices, have been investigated with high resolution Bragg-crystal spectroscopy at 0.13 nm. Recently, x-ray spectroscopic measurements of the dielectronic recombination LMn resonances of W{sup 60+} to W{sup 67+} ions have been preformed and compare well with atomic structure calculations.« less

Inner-shell photoionization and core-hole decay of Xe and XeF2.

PubMed

Southworth, Stephen H; Wehlitz, Ralf; Picón, Antonio; Lehmann, C Stefan; Cheng, Lan; Stanton, John F

2015-06-14

Photoionization cross sections and partial ion yields of Xe and XeF2 from Xe 3d(5/2), Xe 3d(3/2), and F 1s subshells in the 660-740 eV range are compared to explore effects of the F ligands. The Xe 3d-ϵf continuum shape resonances dominate the photoionization cross sections of both the atom and molecule, but prominent resonances appear in the XeF2 cross section due to nominal excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Comparisons of the ion products from the atom and molecule following Xe 3d photoionization show that the charge-state distribution of Xe ions is shifted to lower charge states in the molecule along with production of energetic F(+) and F(2+) ions. This suggests that, in decay of a Xe 3d core hole, charge is redistributed to the F ligands and the system dissociates due to Coulomb repulsion. The ion products from excitation of the F 1s-LUMO resonance are different and show strong increases in the yields of Xe(+) and F(+) ions. The subshell ionization thresholds, the LUMO resonance energies, and their oscillator strengths are calculated by relativistic coupled-cluster methods and agree well with measurements.

Inner-shell photoionization and core-hole decay of Xe and XeF 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Southworth, Stephen H.; Wehlitz, Ralf; Picón, Antonio

2015-06-14

Photoionization cross sections and partial ion yields of Xe and XeF2 from Xe 3d5/2, Xe 3d3/2, and F 1s subshells in the 660–740 eV range are compared to explore effects of the F ligands. The Xe 3d-ϵf continuum shape resonances dominate the photoionization cross sections of both the atom and molecule, but prominent resonances appear in the XeF2 cross section due to nominal excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Comparisons of the ion products from the atom and molecule following Xe 3d photoionization show that the charge-statemore » distribution of Xe ions is shifted to lower charge states in the molecule along with production of energetic F+ and F2+ ions. This suggests that, in decay of a Xe 3d core hole, charge is redistributed to the F ligands and the system dissociates due to Coulomb repulsion. The ion products from excitation of the F 1s-LUMO resonance are different and show strong increases in the yields of Xe+ and F+ ions. The subshell ionization thresholds, the LUMO resonance energies, and their oscillator strengths are calculated by relativistic coupled-cluster methods and agree well with measurements.« less

Remote Sensing of Icy Galilean Moon Surface and Atmospheric Composition Using Low Energy (1 eV-4 keV) Neutral Atom Imaging

NASA Technical Reports Server (NTRS)

Collier, M. R.; Sittler, E.; Chornay, D.; Cooper, J. F.; Coplan, M.; Johnson, R. E.

2004-01-01

We describe a low energy neutral atom imager suitable for composition measurements Europa and other icy Galilean moons in the Jovian magnetosphere. This instrument employs conversion surface technology and is sensitive to either neutrals converted to negative ions, neutrals converted to positive ions and the positive ions themselves depending on the power supply. On a mission such as the Jupiter Icy Moons Orbiter (JIMO), two back-to-back sensors would be flown with separate power supplies fitted to the neutral atom and iodneutral atom sides. This will allow both remote imaging of 1 eV < E < 4 keV neutrals from icy moon surfaces and atmospheres, and in situ measurements of ions at similar energies in the moon ionospheres and Jovian magnetospheric plasma. The instrument provides composition measurements of the neutrals and ions that enter the spectrometer with a mass resolution dependent on the time-of-flight subsystem and capable of resolving molecules. The lower energy neutrals, up to tens of eV, arise from atoms and molecules sputtered off the moon surfaces and out of the moon atmospheres by impacts of more energetic (keV to MeV) ions from the magnetosphere. Direct Simulation Monte Carlo (DSMC) models are used to convert measured neutral abundances to compositional distributions of primary and trace species in the sputtered surfaces and atmospheres. The escaping neutrals can also be detected as ions after photo- or plasma-ionization and pickup. Higher energy, keV neutrals come from charge exchange of magnetospheric ions in the moon atmospheres and provide information on atmospheric structure. At the jovicentric orbits of the icy moons the presence of toroidal gas clouds, as detected at Europa's orbit, provide M e r opportunities to analyze both the composition of neutrals and ions originating from the moon surfaces, and the characteristics of magnetospheric ions interacting with neutral cloud material. Charge exchange of low energy ions near the moons, and directional distributions of the resultant neutrals, allow indirect global mapping of magnetic field structures around the moons. Temporal variation of the magnetic structures can be linked to induced magnetic fields associated with subsurface oceans.

Numerical simulations of primary and secondary hydrogen ENA fluxes at 1 AU

DOE PAGES

Zirnstein, Eric; Heerikhuisen, Jacob; Pogorelov, Nikolai

2012-11-20

The interaction between the solar wind (SW) and the local interstellar medium (LISM) creates energetic neutral atoms (ENAs), mainly Hydrogen (H), at energies similar to ions in the SW. H ENAs are born from charge exchanges between SW protons and LISM H atoms. A large portion of measurable primary ENAs are born in the inner heliosheath (IHS), where the heated and condensed SW plasma has a large thermal component to direct ENAs back toward 1 AU. Secondary ENAs, however, require secondary charge exchanges before being detected at 1 AU. Primary ENAs born in the supersonic and subsonic SW may exitmore » the HP, charge exchange into pick-up ions (PUIs), and charge exchange again to become secondary ENAs. Recent IBEX observations show a ribbon of flux dominating the entire sky. It is possible that the IBEX ribbon is created through secondary charge exchange processes. In this article we present a numerical code that calculates primary and secondary H ENA fluxes by integrating along ENA trajectories. Here we will provide descriptions of the code and preliminary results.« less

Towards laser spectroscopy of the proton-halo candidate boron-8

NASA Astrophysics Data System (ADS)

Maaß, Bernhard; Müller, Peter; Nörtershäuser, Wilfried; Clark, Jason; Gorges, Christian; Kaufmann, Simon; König, Kristian; Krämer, Jörg; Levand, Anthony; Orford, Rodney; Sánchez, Rodolfo; Savard, Guy; Sommer, Felix

2017-11-01

We propose to determine the nuclear charge radius of 8B by high-resolution laser spectroscopy. 8B (t 1/2 = 770 ms) is perhaps the best candidate of a nucleus exhibiting an extended proton wave-function or "one-proton-halo" in a more descriptive picture. Laser spectroscopic measurements of the isotope shift will be used to probe the change in nuclear charge radius along the three boron isotopes 8B, 10B and 11B. The change in nuclear charge radius directly correlates with the extent of the proton wave function. In-flight production and preparation of sufficient yields of 8B ions at low energies is provided by the Argonne Tandem Linac Accelerator System (ATLAS) at Argonne National Laboratory (ANL) in Chicago, IL, USA. Subsequently, the ions will be guided through a charge exchange cell for neutralization and the fluorescence signal of the atoms which interact with the resonant laser light will be detected. The charge radius can then be extracted from the measured isotope shift by employing highly accurate atomic theory calculations of this five-electron system which are carried out presently.

Charge-equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1977-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, is considered. Electron loss of the beam has been taken into account by means of the First Born approximation allowing for the target atom to remain unexcited, or to be excited to all possible states. Electron capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation and collisional inner-shell ionization of the ions has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated.

Cooling atomic ions with visible and infra-red light

NASA Astrophysics Data System (ADS)

Lindenfelser, F.; Marinelli, M.; Negnevitsky, V.; Ragg, S.; Home, J. P.

2017-06-01

We demonstrate the ability to load, cool and detect singly charged calcium ions in a surface electrode trap using only visible and infrared lasers for the trapped-ion control. As opposed to the standard methods of cooling using dipole-allowed transitions, we combine power broadening of a quadrupole transition at 729 nm with quenching of the upper level using a dipole allowed transition at 854 nm. By observing the resulting 393 nm fluorescence we are able to perform background-free detection of the ion. We show that this system can be used to smoothly transition between the Doppler cooling and sideband cooling regimes, and verify theoretical predictions throughout this range. We achieve scattering rates which reliably allow recooling after collision events and allow ions to be loaded from a thermal atomic beam. This work is compatible with recent advances in optical waveguides, and thus opens a path in current technologies for large-scale quantum information processing. In situations where dielectric materials are placed close to trapped ions, it carries the additional advantage of using wavelengths which do not lead to significant charging, which should facilitate high rate optical interfaces between remotely held ions.

Evidence for an ultrafast breakdown of the BeO band structure due to swift argon and xenon ions.

PubMed

Schiwietz, G; Czerski, K; Roth, M; Grande, P L; Koteski, V; Staufenbiel, F

2010-10-29

Auger-electron spectra associated with Be atoms in the pure metal lattice and in the stoichiometric oxide have been investigated for different incident charged particles. For fast incident electrons, for Ar7+ and Ar15+ ions as well as Xe15+ and Xe31+ ions at velocities of 6% to 10% the speed of light, there are strong differences in the corresponding spectral distributions of Be-K Auger lines. These differences are related to changes in the local electronic band structure of BeO on a femtosecond time scale after the passage of highly charged heavy ions.

Derivation of Poisson and Nernst-Planck equations in a bath and channel from a molecular model.

PubMed

Schuss, Z; Nadler, B; Eisenberg, R S

2001-09-01

Permeation of ions from one electrolytic solution to another, through a protein channel, is a biological process of considerable importance. Permeation occurs on a time scale of micro- to milliseconds, far longer than the femtosecond time scales of atomic motion. Direct simulations of atomic dynamics are not yet possible for such long-time scales; thus, averaging is unavoidable. The question is what and how to average. In this paper, we average a Langevin model of ionic motion in a bulk solution and protein channel. The main result is a coupled system of averaged Poisson and Nernst-Planck equations (CPNP) involving conditional and unconditional charge densities and conditional potentials. The resulting NP equations contain the averaged force on a single ion, which is the sum of two components. The first component is the gradient of a conditional electric potential that is the solution of Poisson's equation with conditional and permanent charge densities and boundary conditions of the applied voltage. The second component is the self-induced force on an ion due to surface charges induced only by that ion at dielectric interfaces. The ion induces surface polarization charge that exerts a significant force on the ion itself, not present in earlier PNP equations. The proposed CPNP system is not complete, however, because the electric potential satisfies Poisson's equation with conditional charge densities, conditioned on the location of an ion, while the NP equations contain unconditional densities. The conditional densities are closely related to the well-studied pair-correlation functions of equilibrium statistical mechanics. We examine a specific closure relation, which on the one hand replaces the conditional charge densities by the unconditional ones in the Poisson equation, and on the other hand replaces the self-induced force in the NP equation by an effective self-induced force. This effective self-induced force is nearly zero in the baths but is approximately equal to the self-induced force in and near the channel. The charge densities in the NP equations are interpreted as time averages over long times of the motion of a quasiparticle that diffuses with the same diffusion coefficient as that of a real ion, but is driven by the averaged force. In this way, continuum equations with averaged charge densities and mean-fields can be used to describe permeation through a protein channel.

Carbon Mineralization Using Phosphate and Silicate Ions

NASA Astrophysics Data System (ADS)

Gokturk, H.

2013-12-01

Carbon dioxide (CO2) reduction from combustion of fossil fuels has become an urgent concern for the society due to marked increase in weather related natural disasters and other negative consequences of global warming. CO2 is a highly stable molecule which does not readily interact with other neutral molecules. However it is more responsive to ions due to charge versus quadrupole interaction [1-2]. Ions can be created by dissolving a salt in water and then aerosolizing the solution. This approach gives CO2 molecules a chance to interact with the hydrated salt ions over the large surface area of the aerosol. Ion containing aerosols exist in nature, an example being sea spray particles generated by breaking waves. Such particles contain singly and doubly charged salt ions including Na+, Cl-, Mg++ and SO4--. Depending on the proximity of CO2 to the ion, interaction energy can be significantly higher than the thermal energy of the aerosol. For example, an interaction energy of 0.6 eV is obtained with the sulfate (SO4--) ion when CO2 is the nearest neighbor [2]. In this research interaction between CO2 and ions which carry higher charges are investigated. The molecules selected for the study are triply charged phosphate (PO4---) ions and quadruply charged silicate (SiO4----) ions. Examples of salts which contain such molecules are potassium phosphate (K3PO4) and sodium orthosilicate (Na4SiO4). The research has been carried out with first principle quantum mechanical calculations using the Density Functional Theory method with B3LYP functional and Pople type basis sets augmented with polarization and diffuse functions. Atomic models consist of the selected ions surrounded by water and CO2 molecules. Similar to the results obtained with singly and doubly charged ions [1-2], phosphate and silicate ions attract CO2 molecules. Energy of interaction between the ion and CO2 is 1.6 eV for the phosphate ion and 3.3 eV for the silicate ion. Hence one can expect that the selected ions would enhance the absorption of CO2 into the aerosol even more than the singly or doubly charged ions. Ion containing aerosols also help to catalyze reactions between water and CO2. Hydrated phosphate and silicate ions tend to attract hydrogen atoms from neighboring water molecules to reduce the charged state. When there is CO2 in the vicinity of the ion, the remainder of the water molecule which loses the hydrogen(s) reacts with CO2 to form carbonates. (PO4---) + H2O + CO2 -> (HPO3--) + (HCO3-) (SiO4----) + H2O + CO2 -> (HSiO4---) + (HCO3-) (SiO4----) + H2O + CO2 -> (H2SiO4--) + (CO3--) In conclusion, highly charged phosphate and silicate ions dissolved in water and aerosolized into small droplets can facilitate both the capture and the mineralization of CO2. This method would be especially effective in a CO2 rich environment such as the exhaust gas of a combustion process. [1] H. Gokturk, "Geoengineering with Charged Droplets," AGU Fall Meeting, San Francisco 2011 [2] H. Gokturk, "Atomistic Simulation of Sea Spray Particles," AGU Fall Meeting, San Francisco 2012

Immediate estimation of correlation energy for molecular systems from the partial charges on atoms in the molecule

NASA Astrophysics Data System (ADS)

Kristyán, Sándor

1997-11-01

In the author's previous work (Chem. Phys. Lett. 247 (1995) 101 and Chem. Phys. Lett. 256 (1996) 229) a simple quasi-linear relationship was introduced between the number of electrons, N, participating in any molecular system and the correlation energy: -0.035 ( N - 1) > Ecorr[hartree] > - 0.045( N -1). This relationship was developed to estimate more accurately correlation energy immediately in ab initio calculations by using the partial charges of atoms in the molecule, easily obtained after Hartree-Fock self-consistent field (HF-SCF) calculations. The method is compared to the well-known B3LYP, MP2, CCSD and G2M methods. Correlation energy estimations for negatively (-1) charged atomic ions are also reported.

A New Type of Atom Interferometry for Testing Fundamental Physics

NASA Astrophysics Data System (ADS)

Lorek, Dennis; Lämmerzahl, Claus; Wicht, Andreas

We present a new type of atom interferometer (AI) that provides a tool for ultra-high precision tests of fundamental physics. As an example we present how an AI based on highly charged hydrogen-like atoms is affected by gravitational waves (GW). A qualitative description of the quantum interferometric measurement principle is given, the modifications in the atomic Hamiltonian caused by the GW are presented, and the size of the resulting frequency shifts in hydrogen-like atoms is estimated. For a GW amplitude of h = 10-23 the frequency shift is of the order of 110μHz for an AI based on a 91-fold charged uranium ion. A frequency difference of this size can be resolved by current AIs in 1s.

Calculation of low-Z impurity pellet induced fluxes of charge exchange neutral particles escaping from magnetically confined toroidal plasmas.

PubMed

Goncharov, P R; Ozaki, T; Sudo, S; Tamura, N; Tolstikhina, I Yu; Sergeev, V Yu

2008-10-01

Measurements of energy- and time-resolved neutral hydrogen and helium fluxes from an impurity pellet ablation cloud, referred to as pellet charge exchange or PCX experiments, can be used to study local fast ion energy distributions in fusion plasmas. The estimation of the local distribution function f(i)(E) of fast ions entering the cloud requires knowledge of both the fraction F(0)(E) of incident ions exiting the cloud as neutral atoms and the attenuation factor A(E,rho) describing the loss of fast atoms in the plasma. Determination of A(E,rho), in turn, requires the total stopping cross section sigma(loss) of neutral atoms in the plasma and the Jacobian reflecting the measurement geometry and the magnetic surface shape. The obtained functions F(0)(E) and A(E,rho) enter multiplicatively into the probability density for escaping neutral particle kinetic energy. A general calculation scheme has been developed and realized as a FORTRAN code, which is to be applied for the calculation of f(i)(E) from PCX experimental results obtained with low-Z impurity pellets.

Stopping power of dense plasmas: The collisional method and limitations of the dielectric formalism.

PubMed

Clauser, C F; Arista, N R

2018-02-01

We present a study of the stopping power of plasmas using two main approaches: the collisional (scattering theory) and the dielectric formalisms. In the former case, we use a semiclassical method based on quantum scattering theory. In the latter case, we use the full description given by the extension of the Lindhard dielectric function for plasmas of all degeneracies. We compare these two theories and show that the dielectric formalism has limitations when it is used for slow heavy ions or atoms in dense plasmas. We present a study of these limitations and show the regimes where the dielectric formalism can be used, with appropriate corrections to include the usual quantum and classical limits. On the other hand, the semiclassical method shows the correct behavior for all plasma conditions and projectile velocity and charge. We consider different models for the ion charge distributions, including bare and dressed ions as well as neutral atoms.

Relativistic calculations of atomic properties

NASA Astrophysics Data System (ADS)

Kaur, Jasmeet; Sahoo, B. K.; Arora, Bindiya

2017-04-01

Singly charged ions are engaging candidates in many areas of Physics. They are especially important in astrophysics for evaluating the radiative properties of stellar objects, in optical frequency standards and for fundamental physics studies such as searches for permanent electric dipole moments and atomic parity violation. Interpretation of these experiments often requires a knowledge of their transition wavelengths and electric dipole amplitudes. In this work, we discuss the calculation of various properties of alkaline earth ions. The relativistic all-order SD method in which all single and double excitations of the Dirac-Fock wave function are included, is used to calculate these atomic properties. We use this method for evaluation of electric dipole matrix elements of alkaline earth ions. Combination of these matrix elements with experimental energies allow to obtain the polarizabilities of ground and excited states of ions. We discuss the applications of estimated polarizabiities as a function of imaginary frequencies in the calculations of long-range atom-ion interactions. We have also located the magic wavelengths for nS1 / 2 - nD3 / 2 , 5 / 2 transitions of alkaline earth ions. These calculated properties will be highly valuable to atomic and astrophysics community. UGC-BSR Grant No. F.7-273/2009/BSR.

SERENA: A suite of four instruments (ELENA, STROFIO, PICAM and MIPA) on board BepiColombo-MPO for particle detection in the Hermean environment

NASA Astrophysics Data System (ADS)

Orsini, S.; Livi, S.; Torkar, K.; Barabash, S.; Milillo, A.; Wurz, P.; di Lellis, A. M.; Kallio, E.; The Serena Team

2010-01-01

'Search for Exospheric Refilling and Emitted Natural Abundances' (SERENA) is an instrument package that will fly on board the BepiColombo/Mercury Planetary Orbiter (MPO). It will investigate Mercury's complex particle environment that is composed of thermal and directional neutral atoms (exosphere) caused by surface release and charge-exchange processes, and of ionized particles caused by photo-ionization of neutrals as well by charge exchange and surface release processes. In order to investigate the structure and dynamics of the environment, an in-situ analysis of the key neutral and charged components is necessary, and for this purpose the SERENA instrument shall include four units: two neutral particle analyzers (Emitted Low Energy Neutral Atoms (ELENA) sensor and Start from a Rotating FIeld mass spectrometer (STROFIO)) and two ion spectrometers (Miniature Ion Precipitation Analyzer (MIPA) and Planetary Ion Camera (PICAM)). The scientific merits of SERENA are presented, and the basic characteristics of the four units are described, with a focus on novel technological aspects.

Energetic neutral particles from Jupiter and Saturn

NASA Astrophysics Data System (ADS)

Cheng, A. F.

1986-04-01

The Voyager 1 spacecraft has detected energetic neutral particles escaping from the magnetospheres of Jupiter and Saturn. These energetic neutrals are created in charge exchange reactions between radiation belt ions and ambient atoms or molecules in the magnetosphere. If the Io torus is assumed to be the dominant Jovian source region for energetic neutrals, the Voyager observations can be used to infer upper limits to the average ion intensities there below about 200 keV. No readily interpretable in-situ measurements are available in the Io torus at these energies. The middle and outer Jovian magnetospheres may also be a significant source of energetic neutrals. At Saturn, the observed neutral particle count rates are too high to be explained by charge exchange between fast protons and H atoms of the Titan torus. Most of the energetic neutrals may be produced by charge exchanges between heavy ions and a neutral cloud containing H2O in Saturn's inner magnetosphere. If so, the Voyager measurements of energetic neutral fluxes would be the first detected emissions from this region of Saturn's magnetosphere.

Insight into induced charges at metal surfaces and biointerfaces using a polarizable Lennard-Jones potential.

PubMed

Geada, Isidro Lorenzo; Ramezani-Dakhel, Hadi; Jamil, Tariq; Sulpizi, Marialore; Heinz, Hendrik

2018-02-19

Metallic nanostructures have become popular for applications in therapeutics, catalysts, imaging, and gene delivery. Molecular dynamics simulations are gaining influence to predict nanostructure assembly and performance; however, instantaneous polarization effects due to induced charges in the free electron gas are not routinely included. Here we present a simple, compatible, and accurate polarizable potential for gold that consists of a Lennard-Jones potential and a harmonically coupled core-shell charge pair for every metal atom. The model reproduces the classical image potential of adsorbed ions as well as surface, bulk, and aqueous interfacial properties in excellent agreement with experiment. Induced charges affect the adsorption of ions onto gold surfaces in the gas phase at a strength similar to chemical bonds while ions and charged peptides in solution are influenced at a strength similar to intermolecular bonds. The proposed model can be applied to complex gold interfaces, electrode processes, and extended to other metals.

Ion-induced particle desorption in time-of-flight medium energy ion scattering

NASA Astrophysics Data System (ADS)

Lohmann, S.; Primetzhofer, D.

2018-05-01

Secondary ions emitted from solids upon ion impact are studied in a time-of-flight medium energy ion scattering (ToF-MEIS) set-up. In order to investigate characteristics of the emission processes and to evaluate the potential for surface and thin film analysis, experiments employing TiN and Al samples were conducted. The ejected ions exhibit a low initial kinetic energy of a few eV, thus, requiring a sufficiently high acceleration voltage for detection. Molecular and atomic ions of different charge states originating both from surface contaminations and the sample material are found, and relative yields of several species were determined. Experimental evidence that points towards a predominantly electronic sputtering process is presented. For emitted Ti target atoms an additional nuclear sputtering component is suggested.

Deep Space 1 Ion Engine

NASA Image and Video Library

2002-12-21

This image of a xenon ion engine prototype, photographed through a port of the vacuum chamber where it was being tested at NASA's Jet Propulsion Laboratory, shows the faint blue glow of charged atoms being emitted from the engine. The engine is now in an ongoing extended- life test, in a vacuum test chamber at JPL, and has run for almost 500 days (12,000 hours) and is scheduled to complete nearly 625 days (15,000 hours) by the end of 2001. A similar engine powers the New Millennium Program's flagship mission, Deep Space 1, which uses the ion engine in a trip through the solar system. The engine, weighing 17.6 pounds (8 kilograms), is 15.7 inches (40 centimeters) in diameter and 15.7 inches long. The actual thrust comes from accelerating and expelling positively charged xenon atoms, or ions. While the ions are fired in great numbers out the thruster at more than 110,000 kilometers (68,000 miles) per hour, their mass is so low that the engine produces a gentle thrust of only 90 millinewtons (20-thousandths of a pound). http://photojournal.jpl.nasa.gov/catalog/PIA04238

Effects of dissolucytotic gold ions on recovering brain lesions.

PubMed

Danscher, Gorm; Larsen, Agnete

2010-04-01

Recent experimental research has shown that metallic gold releases charged gold atoms when placed intracerebrally and that the liberated gold ions affect inflammation in the brain. The observations suggest that metallic gold can be used as a safe suppressor of inflammation in the central nervous system.

Spectral Diagnostics of Galactic and Stellar X-Ray Emission from Charge Exchange Recombination

NASA Technical Reports Server (NTRS)

Wargelin, B.

2002-01-01

The proposed research uses the electron beam ion trap at the Lawrence Livermore National Laboratory (LLNL) to study X-ray emission from charge-exchange recombination of highly charged ions with neutral gases. The resulting data fill a void in existing experimental and theoretical understanding of this atomic physics process, and are needed to explain all or part of the observed X-ray emission from the soft X-ray background, stellar winds, the Galactic Center, supernova ejecta, and photoionized nebulae. Progress made during the first year of the grant is described, as is work planned for the second year.

Background of the completed research; relevances to solar physics

NASA Technical Reports Server (NTRS)

Sellin, I. A.

1973-01-01

Research activities reported consider the atomic structures of highly stripped heavy ions and their modes of formation and destruction in collisions. The lifetime of the metastable 2 3p1 state of the two electron ion F-7(+) was determined by measuring the radiative decay of an excited helium-like fluorine beam, Metastable state quenching measurements were performed on a helium-like ion to obtain the 1 1S0 to 2 3p2 transition probability. Exponential exchange state dependence of X-ray production cross sections was studied in heavy target atoms during collisions with light charged particles.

Satellite Charge Control with Lithium Ion Source and Electron Emission

DTIC Science & Technology

1990-12-01

for the spacecraft charge control. C. THERMIONIC ELECTRON EMISSION Electrons may be emitted by surfaces at high temperature in a process, called...data in the high voltage region and 1300 to 1600 °K temperature range may be fitted to the following equation, for a 50 % lithium sample: log01 =logos...in Figure 15, is similar to a high - temperature quartz structure, yet differs from it in that half of the silicon atoms are repiaced by aluminum atoms

The pair-production channel in atomic processes

NASA Astrophysics Data System (ADS)

Belkacem, Ali; Sørensen, Allan H.

2006-06-01

Assisted by the creation of electron-positron pairs, new channels for ionization, excitation, and charge transfer open in atomic collisions when the energy is raised to relativistic values. At extreme energies these pair-production channels usually dominate the "traditional" contributions to cross sections that involve only "positive-energy" electrons. An extensive body of theoretical and experimental work has been performed over the last two decades to investigate charge-changing processes catalyzed by pair production in relativistic heavy ion collisions. We review some of these studies.

Investigation and Development of Advanced Surface Microanalysis Techniques and Methods

DTIC Science & Technology

1983-04-01

descriminates against isobars since each of the isobaric species will have a different atomic number or Z and, therefore, will be stripped of its...allow descrimination between two elements at the same mass but which have different atomic numbers. Multiply-charged ions are not produced during the

Effect of charge and composition on the structural fluxionality and stability of nine atom tin-bismuth Zintl analogues.

PubMed

Gupta, Ujjwal; Reber, Arthur C; Clayborne, Penee A; Melko, Joshua J; Khanna, Shiv N; Castleman, A W

2008-12-01

Synergistic studies of bismuth doped tin clusters combining photoelectron spectra with first principles theoretical investigations establish that highly charged Zintl ions, observed in the condensed phase, can be stabilized as isolated gas phase clusters through atomic substitution that preserves the overall electron count but reduces the net charge and thereby avoids instability because of coulomb repulsion. Mass spectrometry studies reveal that Sn(8)Bi(-), Sn(7)Bi(2)(-), and Sn(6)Bi(3)(-) exhibit higher abundances than neighboring species, and photoelectron spectroscopy show that all of these heteroatomic gas phase Zintl analogues (GPZAs) have high adiabatic electron detachment energies. Sn(6)Bi(3)(-) is found to be a particularly stable cluster, having a large highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap. Theoretical calculations demonstrate that the Sn(6)Bi(3)(-) cluster is isoelectronic with the well know Sn(9)(-4) Zintl ion; however, the fluxionality reported for Sn(9)(-4) is suppressed by substituting Sn atoms with Bi atoms. Thus, while the electronic stability of the clusters is dominated by electron count, the size and position of the atoms affects the dynamics of the cluster as well. Substitution with Bi enlarges the cage compared with Sn(9)(-4) making it favorable for endohedral doping, findings which suggest that these cages may find use for building blocks of cluster assembled materials.

Global, Energy-Dependent Ring Current Response During Two Large Storms

NASA Astrophysics Data System (ADS)

Goldstein, J.; Angelopoulos, V.; Burch, J. L.; De Pascuale, S.; Fuselier, S. A.; Genestreti, K. J.; Kurth, W. S.; LLera, K.; McComas, D. J.; Reeves, G. D.; Spence, H. E.; Valek, P. W.

2015-12-01

Two recent large (~200 nT) geomagnetic storms occurred during 17--18 March 2015 and 22--23 June 2015. The global, energy-dependent ring current response to these two extreme events is investigated using both global imaging and multi-point in situ observations. Energetic neutral atom (ENA) imaging by the Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission provides a global view of ring current ions. Local measurements are provided by two multi-spacecraft missions. The two Van Allen Probes measure in situ plasma (including ion composition) and fields at ring current and plasmaspheric L values. The recently launched Magnetospheric Multiscale (MMS) comprises four spacecraft that have just begun to measure particles (including ion composition) and fields at outer magnetospheric L-values. We analyze the timing and energetics of the stormtime evolution of ring current ions, both trapped and precipitating, using TWINS ENA images and in situ data by the Van Allen Probes and MMS.

Atomic physics effects on tokamak edge drift-tearing modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

Atomic physics effects on tokamak edge drift-tearing modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

The ATLAS multi-user upgrade and potential applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mustapha, B.; Nolen, J. A.; Savard, G.

With the recent integration of the CARIBU-EBIS charge breeder into the ATLAS accelerator system to provide for more pure and efficient charge breeding of radioactive beams, a multi-user upgrade of the ATLAS facility is being proposed to serve multiple users simultaneously. ATLAS was the first superconducting ion linac in the world and is the US DOE low-energy Nuclear Physics National User Facility. The proposed upgrade will take advantage of the continuous-wave nature of ATLAS and the pulsed nature of the EBIS charge breeder in order to simultaneously accelerate two beams with very close mass-to-charge ratios; one stable from the existingmore » ECR ion source and one radioactive from the newly commissioned EBIS charge breeder. In addition to enhancing the nuclear physics program, beam extraction at different points along the linac will open up the opportunity for other potential applications; for instance, material irradiation studies at ~ 1 MeV/u and isotope production at ~ 6 MeV/u or at the full ATLAS energy of ~ 15 MeV/u. The concept and proposed implementation of the ATLAS multi-user upgrade will be presented. Future plans to enhance the flexibility of this upgrade will also be presented.« less

The ATLAS multi-user upgrade and potential applications

NASA Astrophysics Data System (ADS)

Mustapha, B.; Nolen, J. A.; Savard, G.; Ostroumov, P. N.

2017-12-01

With the recent integration of the CARIBU-EBIS charge breeder into the ATLAS accelerator system to provide for more pure and efficient charge breeding of radioactive beams, a multi-user upgrade of the ATLAS facility is being proposed to serve multiple users simultaneously. ATLAS was the first superconducting ion linac in the world and is the US DOE low-energy Nuclear Physics National User Facility. The proposed upgrade will take advantage of the continuous-wave nature of ATLAS and the pulsed nature of the EBIS charge breeder in order to simultaneously accelerate two beams with very close mass-to-charge ratios; one stable from the existing ECR ion source and one radioactive from the newly commissioned EBIS charge breeder. In addition to enhancing the nuclear physics program, beam extraction at different points along the linac will open up the opportunity for other potential applications; for instance, material irradiation studies at ~1 MeV/u, isotope production and radiobiological studies at ~6 MeV/u and at the full ATLAS energy of ~15 MeV/u. The concept and proposed implementation of the ATLAS multi-user upgrade will be discussed. Future plans to enhance the flexibility of this upgrade will be presented.

Delayed bunching for multi-reflection time-of-flight mass separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenbusch, M.; Marx, G.; Schweikhard, L.

2015-06-29

Many experiments are handicapped when the ion sources do not only deliver the ions of interest but also contaminations, i.e., unwanted ions of similar mass. In the recent years, multi-reflection time-of-flight mass separation has become a promising method to isolate the ions of interest from the contaminants, in particular for measurements with low-energy short-lived nuclides. To further improve the performance of multi-reflection mass separators with respect to the limitations by space-charge effects, the simultaneously trapped ions are spatially widely distributed in the apparatus. Thus, the ions can propagate with reduced Coulomb interactions until, finally, they are bunched by a changemore » in the trapping conditions for high-resolution mass separation. Proof-of-principle measurements are presented.« less

Optical transitions in highly charged californium ions with high sensitivity to variation of the fine-structure constant.

PubMed

Berengut, J C; Dzuba, V A; Flambaum, V V; Ong, A

2012-08-17

We study electronic transitions in highly charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, α. The transitions are in the optical range despite the large ionization energies because they lie on the level crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf(16+) is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf(16+) has very large nuclear charge and large ionization energy, resulting in the largest α sensitivity seen in atomic systems. The lines include positive and negative shifters.

Laser ion source for multi-nucleon transfer reaction products

NASA Astrophysics Data System (ADS)

Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

2015-06-01

We have developed a laser ion source for the target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. The operation principle of the source is based on the in-gas laser ionization and spectroscopy (IGLIS) approach. In the source TLFs are thermalized and neutralized in high pressure and high purity argon gas, and are extracted after being selectively re-ionized in a multi-step laser resonance ionization process. The laser ion source has been implemented at the KEK Isotope Separation System (KISS) for β-decay spectroscopy of neutron-rich isotopes with N = 126 of nuclear astrophysical interest. The simulations of gas flow and ion-beam optics have been performed to optimize the gas cell for efficient thermalization and fast transporting the TLFs, and the mass-separator for efficient transport with high mass-resolving power, respectively. To confirm the performances expected at the design stage, off-line experiments have been performed by using 56Fe atoms evaporated from a filament in the gas cell. The gas-transport time of 230 ms in the argon cell and the measured KISS mass-resolving power of 900 are consistent with the designed values. The high purity of the gas-cell system, which is extremely important for efficient and highly-selective production of laser ions, was achieved and confirmed from the mass distribution of the extracted ions. After the off-line tests, on-line experiments were conducted by directly injecting energetic 56Fe beam into the gas cell. After thermalization of the injected 56Fe beam, laser-produced singly-charged 56Fe+ ions were extracted. The extraction efficiency and selectivity of the gas cell in the presence of plasma induced by 56Fe beam injection as well as the time profile of the extracted ions were investigated; extraction efficiency of 0.25%, a beam purity of >99% and an extraction time of 270 ms. It has been confirmed that the performance of the KISS laser ion source is satisfactory to start the measurements of lifetimes of the β-decayed nuclei with N = 126 .

Total photoionization cross sections of atomic oxygen from threshold to 44.3 A

NASA Technical Reports Server (NTRS)

Angel, G. C.; Samson, James A. R.

1988-01-01

Synchrotron radiation was used to obtain the relative photoionization cross section of atomic oxygen for the production of singly charged ions over the 44.3-910.5-A wavelength range. Measurement of the contribution of multiple ionization to the cross sections has made possible the determination of total photoionization cross sections below 250 A. The series of autoionizing resonances leading to the 4P state of the oxygen ion has been observed using an ionization-type experimental procedure for the first time.

Self-regenerating column chromatography

DOEpatents

Park, Woo K.

1995-05-30

The present invention provides a process for treating both cations and anions by using a self-regenerating, multi-ionic exchange resin column system which requires no separate regeneration steps. The process involves alternating ion-exchange chromatography for cations and anions in a multi-ionic exchange column packed with a mixture of cation and anion exchange resins. The multi-ionic mixed-charge resin column works as a multi-function column, capable of independently processing either cationic or anionic exchange, or simultaneously processing both cationic and anionic exchanges. The major advantage offered by the alternating multi-function ion exchange process is the self-regeneration of the resins.

Long-range Coulomb forces and localized bonds.

PubMed

Preiser; Lösel; Brown; Kunz; Skowron

1999-10-01

The ionic model is shown to be applicable to all compounds in which the atoms carry a net charge and their electron density is spherically symmetric regardless of the covalent character of the bonding. By examining the electric field generated by an array of point charges placed at the positions of the ions in over 40 inorganic compounds, we show that the Coulomb field naturally partitions itself into localized regions (bonds) which are characterized by the electric flux that links neighbouring ions of opposite charge. This flux is identified with the bond valence, and Gauss' law with the valence-sum rule, providing a secure theoretical foundation for the bond-valence model. The localization of the Coulomb field provides an unambiguous definition of coordination number and our calculations show that, in addition to the expected primary coordination sphere, there are a number of weak bonds between cations and the anions in the second coordination sphere. Long-range Coulomb interactions are transmitted through the crystal by the application of Gauss' law at each of the intermediate atoms. Bond fluxes have also been calculated for compounds containing ions with non-spherical electron densities (e.g. cations with stereoactive lone electron pairs). In these cases the point-charge model continues to describe the distant field, but multipoles must be added to the point charges to give the correct local field.

Physics Division annual review, 1 April 1975--31 March 1976. [ANL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garvey, G. T.

1976-01-01

An overview is given of Physics Division activities in the following areas: the heavy-ion booster; medium-energy physics; heavy-ion physics; low-energy charged-particle physics; accelerator operations; neutron physics; theoretical nuclear physics, and atomic and molecular physics. A bibliography of publications amounts to 27 pages. (RWR)

Highly sensitive solids mass spectrometer uses inert-gas ion source

NASA Technical Reports Server (NTRS)

1966-01-01

Mass spectrometer provides a recorded analysis of solid material surfaces and bulk. A beam of high-energy inert-gas ions bombards the surface atoms of a sample and converts a percentage into an ionized vapor. The mass spectrum analyzer separates the vapor ionic constituents by mass-to-charge ratio.

Dust Particle Dynamics in The Presence of Highly Magnetized Plasmas

NASA Astrophysics Data System (ADS)

Lynch, Brian; Konopka, Uwe; Thomas, Edward; Merlino, Robert; Rosenberg, Marlene

2016-10-01

Complex plasmas are four component plasmas that contain, in addition to the usual electrons, ions, and neutral atoms, macroscopic electrically charged (nanometer to micrometer) sized ``dust'' particles. These macroscopic particles typically obtain a net negative charge due to the higher mobility of electrons compared to that of ions. Because the electrons, ions, and dust particles are charged, their dynamics may be significantly modified by the presence of electric and magnetic fields. Possible consequences of this modification may be the charging rate and the equilibrium charge. For example, in the presence of a strong horizontal magnetic field (B >1 Tesla), it may be possible to observe dust particle gx B deflection and, from that deflection, determine the dust grain charge. In this poster, we present recent data from performing multiple particle dropping experiments to characterize the g x B deflection in the Magnetized Dusty Plasma Experiment (MDPX). This work is supported by funding from the U. S. Department of Energy Grant Number DE - SC0010485 and the NASA/Jet Propulsion Laboratory, JPL-1543114.

Deceleration, precooling, and multi-pass stopping of highly charged ions in Be{sup +} Coulomb crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmöger, L., E-mail: lisa.schmoeger@mpi-hd.mpg.de; Schwarz, M.; Versolato, O. O.

2015-10-15

Preparing highly charged ions (HCIs) in a cold and strongly localized state is of particular interest for frequency metrology and tests of possible spatial and temporal variations of the fine structure constant. Our versatile preparation technique is based on the generic modular combination of a pulsed ion source with a cryogenic linear Paul trap. Both instruments are connected by a compact beamline with deceleration and precooling properties. We present its design and commissioning experiments regarding these two functionalities. A pulsed buncher tube allows for the deceleration and longitudinal phase-space compression of the ion pulses. External injection of slow HCIs, specificallymore » Ar{sup 13+}, into the linear Paul trap and their subsequent retrapping in the absence of sympathetic cooling is demonstrated. The latter proved to be a necessary prerequisite for the multi-pass stopping of HCIs in continuously laser-cooled Be{sup +} Coulomb crystals.« less

Discrimination of ionic species from broad-beam ion sources

NASA Technical Reports Server (NTRS)

Anderson, J. R.

1993-01-01

The performance of a broad-beam, three-grid, ion extraction system incorporating radio frequency (RF) mass discrimination was investigated experimentally. This testing demonstrated that the system, based on a modified single-stage Bennett mass spectrometer, can discriminate between ionic species having about a 2-to-1 mass ratio while producing a broad-beam of ions with low kinetic energy (less than 15 eV). Testing was conducted using either argon and krypton ions or atomic and diatomic oxygen ions. A simple one-dimensional model, which ignores magnetic field and space-charge effects, was developed to predict the species separation capabilities as well as the kinetic energies of the extracted ions. The experimental results correlated well with the model predictions. This RF mass discrimination system can be used in applications where both atomic and diatomic ions are produced, but a beam of only one of the species is desired. An example of such an application is a 5 eV atomic oxygen source. This source would produce a beam of atomic oxygen with 5 eV kinetic energy, which would be directed onto a material specimen, to simulate the interaction between the surface of a satellite and the rarefied atmosphere encountered in low-Earth orbit.

Superior ionic and electronic properties of ReN2 monolayers for Na-ion battery electrodes.

PubMed

Zhang, Shi-Hao; Liu, Bang-Gui

2018-08-10

Excellent monolayer electrode materials can be used to design high-performance alkali-metal-ion batteries. Here, we propose two-dimensional ReN 2 monolayers as superior sodium-ion battery materials. Our total energy optimization results in a buckled tetragonal structure for the ReN 2 monolayer, and our phonon spectrum and elastic moduli prove that it is dynamically and mechanically stable. Further investigations show that it is metallic and still keeps its metallic feature after the adsorption of Na or K atoms, and the adsorption of Na (or K) atoms changes the lattice parameters by 3.2% (or 3.8%) at most. Its maximum capacity reaches 751 mA h g -1 for Na-ion batteries or 250 mA h g -1 for K-ion batteries, and the diffusion barrier is only 0.027 eV for the Na atom or 0.127 eV for the K atom. The small lattice changes, high storage capacity, metallic feature, and extremely low ion diffusion barriers make the ReN 2 monolayers a superior electrode material for Na-ion rechargeable batteries with ultrafast charging/discharging processes.

Conduction Properties of KcsA Measured Using Brownian Dynamics with Flexible Carbonyl Groups in the Selectivity Filter

PubMed Central

Chung, Shin-Ho; Corry, Ben

2007-01-01

In the narrow segment of an ion conducting pathway, it is likely that a permeating ion influences the positions of the nearby atoms that carry partial or full electronic charges. Here we introduce a method of incorporating the motion of charged atoms lining the pore into Brownian dynamics simulations of ion conduction. The movements of the carbonyl groups in the selectivity filter of the KcsA channel are calculated explicitly, allowing their bond lengths, bond angles, and dihedral angels to change in response to the forces acting upon them. By systematically changing the coefficients of bond stretching and of angle bending, the carbon and oxygen atoms can be made to fluctuate from their fixed positions by varying mean distances. We show that incorporating carbonyl motion in this way does not alter the mechanism of ion conduction and only has a small influence on the computed current. The slope conductance of the channel increases by ∼25% when the root mean-square fluctuations of the carbonyl groups are increased from 0.01 to 0.61 Å. The energy profiles and the number of resident ions in the channel remain unchanged. The method we utilized here can be extended to allow the movement of glutamate or aspartate side chains lining the selectivity filters of other ionic channels. PMID:17434934

Conduction properties of KcsA measured using brownian dynamics with flexible carbonyl groups in the selectivity filter.

PubMed

Chung, Shin-Ho; Corry, Ben

2007-07-01

In the narrow segment of an ion conducting pathway, it is likely that a permeating ion influences the positions of the nearby atoms that carry partial or full electronic charges. Here we introduce a method of incorporating the motion of charged atoms lining the pore into Brownian dynamics simulations of ion conduction. The movements of the carbonyl groups in the selectivity filter of the KcsA channel are calculated explicitly, allowing their bond lengths, bond angles, and dihedral angels to change in response to the forces acting upon them. By systematically changing the coefficients of bond stretching and of angle bending, the carbon and oxygen atoms can be made to fluctuate from their fixed positions by varying mean distances. We show that incorporating carbonyl motion in this way does not alter the mechanism of ion conduction and only has a small influence on the computed current. The slope conductance of the channel increases by approximately 25% when the root mean-square fluctuations of the carbonyl groups are increased from 0.01 to 0.61 A. The energy profiles and the number of resident ions in the channel remain unchanged. The method we utilized here can be extended to allow the movement of glutamate or aspartate side chains lining the selectivity filters of other ionic channels.

Point charge representation of multicenter multipole moments in calculation of electrostatic properties

NASA Technical Reports Server (NTRS)

Sokalski, W. A.; Shibata, M.; Ornstein, R. L.; Rein, R.

1993-01-01

Distributed Point Charge Models (PCM) for CO, (H2O)2, and HS-SH molecules have been computed from analytical expressions using multi-center multipole moments. The point charges (set of charges including both atomic and non-atomic positions) exactly reproduce both molecular and segmental multipole moments, thus constituting an accurate representation of the local anisotropy of electrostatic properties. In contrast to other known point charge models, PCM can be used to calculate not only intermolecular, but also intramolecular interactions. Comparison of these results with more accurate calculations demonstrated that PCM can correctly represent both weak and strong (intramolecular) interactions, thus indicating the merit of extending PCM to obtain improved potentials for molecular mechanics and molecular dynamics computational methods.

Ions with low charges in the solar wind as measured by SWICS on board Ulysses. [Solar Wind Ion Composition Spectrometer

NASA Technical Reports Server (NTRS)

Geiss, J.; Ogilvie, K. W.; Von Steiger, R.; Mall, U.; Gloeckler, G.; Galvin, A. B.; Ipavich, F.; Wilken, B.; Gliem, F.

1992-01-01

We present new data on rare ions in the solar wind. Using the Ulysses-SWICS instrument with its very low background we have searched for low-charge ions during a 6-d period of low-speed solar wind and established sensitive upper limits for many species. In the solar wind, we found He(1+)/He(2+) of less than 5 x 10 exp -4. This result and the charge state distributions of heavier elements indicate that all components of the investigated ion population went through a regular coronal expansion and experienced the typical electron temperatures of 1 to 2 million Kelvin. We argue that the virtual absence of low-charge ions demonstrates a very low level of nonsolar contamination in the source region of the solar wind sample we studied. Since this sample showed the FlP effect typical for low-speed solar wind, i.e., an enhancement in the abundances of elements with low first ionization potential, we conclude that this enhancement was caused by an ion-atom separation mechanism operating near the solar surface and not by foreign material in the corona.

Inner-shell photoionization and core-hole decay of Xe and XeF{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Southworth, Stephen H.; Picón, Antonio; Lehmann, C. Stefan

2015-06-14

Photoionization cross sections and partial ion yields of Xe and XeF{sub 2} from Xe 3d{sub 5/2}, Xe 3d{sub 3/2}, and F 1s subshells in the 660–740 eV range are compared to explore effects of the F ligands. The Xe 3d-ϵf continuum shape resonances dominate the photoionization cross sections of both the atom and molecule, but prominent resonances appear in the XeF{sub 2} cross section due to nominal excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Comparisons of the ion products from the atom and molecule following Xe 3d photoionizationmore » show that the charge-state distribution of Xe ions is shifted to lower charge states in the molecule along with production of energetic F{sup +} and F{sup 2+} ions. This suggests that, in decay of a Xe 3d core hole, charge is redistributed to the F ligands and the system dissociates due to Coulomb repulsion. The ion products from excitation of the F 1s-LUMO resonance are different and show strong increases in the yields of Xe{sup +} and F{sup +} ions. The subshell ionization thresholds, the LUMO resonance energies, and their oscillator strengths are calculated by relativistic coupled-cluster methods and agree well with measurements.« less

A unified formulation of dichroic signals using the Borrmann effect and twisted photon beams.

PubMed

Collins, Stephen P; Lovesey, Stephen W

2018-05-21

Dichroic X-ray signals derived from the Borrmann effect and a twisted photon beam with topological charge l = 1 are formulated with an effective wavevector. The unification applies for non-magnetic and magnetic materials. Electronic degrees of freedom associated with an ion are encapsulated in multipoles previously used to interpret conventional dichroism and Bragg diffraction enhanced by an atomic resonance. A dichroic signal exploiting the Borrmann effect with a linearly polarized beam presents charge-like multipoles that include a hexadecapole. A difference between dichroic signals obtained with a twisted beam carrying spin polarization (circular polarization) and opposite winding numbers presents charge-like atomic multipoles, whereas a twisted beam carrying linear polarization alone presents magnetic (time-odd) multipoles. Charge-like multipoles include a quadrupole, and magnetic multipoles include a dipole and an octupole. We discuss the practicalities and relative merits of spectroscopy exploiting the two remarkably closely-related processes. Signals using beams with topological charges l ≥ 2 present additional atomic multipoles.

Focused beams of fast neutral atoms in glow discharge plasma

NASA Astrophysics Data System (ADS)

Grigoriev, S. N.; Melnik, Yu. A.; Metel, A. S.; Volosova, M. A.

2017-06-01

Glow discharge with electrostatic confinement of electrons in a vacuum chamber allows plasma processing of conductive products in a wide pressure range of p = 0.01 - 5 Pa. To assist processing of a small dielectric product with a concentrated on its surface beam of fast neutral atoms, which do not cause charge effects, ions from the discharge plasma are accelerated towards the product and transformed into fast atoms. The beam is produced using a negatively biased cylindrical or a spherical grid immersed in the plasma. Ions accelerated by the grid turn into fast neutral atoms at p > 0.1 Pa due to charge exchange collisions with gas atoms in the space charge sheaths adjoining the grid. The atoms form a diverging neutral beam and a converging beam propagating from the grid in opposite directions. The beam propagating from the concave surface of a 0.24-m-wide cylindrical grid is focused on a target within a 10-mm-wide stripe, and the beam from the 0.24-m-diameter spherical grid is focused within a 10-mm-diameter circle. At the bias voltage U = 5 kV and p ˜ 0.1 Pa, the energy of fast argon atoms is distributed continuously from zero to eU ˜ 5 keV. The pressure increase to 1 Pa results in the tenfold growth of their equivalent current and a decrease in the mean energy by an order of magnitude, which substantially raises the efficiency of material etching. Sharpening by the beam of ceramic knife-blades proved that the new method for the generation of concentrated fast atom beams can be effectively used for the processing of dielectric materials in vacuum.

Dissociation of heme from gaseous myoglobin ions studied by infrared multiphoton dissociation spectroscopy and Fourier-transform ion cyclotron resonance mass spectrometry

NASA Astrophysics Data System (ADS)

Wang, Yi-Sheng; Sabu, Sahadevan; Wei, Shih-Chia; Josh Kao, C.-M.; Kong, Xianglei; Liau, Shing-Chih; Han, Chau-Chung; Chang, Huan-Cheng; Tu, Shih-Yu; Kung, A. H.; Zhang, John Z. H.

2006-10-01

Detachment of heme prosthetic groups from gaseous myoglobin ions has been studied by collision-induced dissociation and infrared multiphoton dissociation in combination with Fourier-transform ion cyclotron resonance mass spectrometry. Multiply charged holomyoglobin ions (hMbn +) were generated by electrospray ionization and transferred to an ion cyclotron resonance cell, where the ions of interest were isolated and fragmented by either collision with Ar atoms or irradiation with 3μm photons, producing apomyoglobin ions (aMbn +). Both charged heme loss (with [Fe(III)-heme]+ and aMb(n-1)+ as the products) and neutral heme loss (with [Fe(II)-heme] and aMbn + as the products) were detected concurrently for hMbn + produced from a myoglobin solution pretreated with reducing reagents. By reference to Ea=0.9eV determined by blackbody infrared radiative dissociation for charged heme loss of ferric hMbn +, an activation energy of 1.1eV was deduced for neutral heme loss of ferrous hMbn + with n =9 and 10.

Ion temperature profiles in front of a negative planar electrode studied by a one-dimensional two-fluid model

NASA Astrophysics Data System (ADS)

Gyergyek, T.; Kovačič, J.

2016-06-01

Plasma-wall transition is studied by a one-dimensional steady state two-fluid model. Continuity and momentum exchange equations are used for the electrons, while the continuity, momentum exchange, and energy transport equation are used for the ions. Electrons are assumed to be isothermal. The closure of ion equations is made by the assumption that the heat flux is zero. The model equations are solved for potential, ion and electron density, and velocity and ion temperature as independent variables. The model includes coulomb collisions between ions and electrons and charge exchange collisions between ions and neutral atoms of the same species and same mass. The neutral atoms are assumed to be essentially at rest. The model is solved for finite ratio ɛ = /λ D L between the Debye length and λD and ionization length L in the pre-sheath and in the sheath at the same time. Charge exchange collisions heat the ions in the sheath and the pre-sheath. Even a small increase of the frequency of charge exchange collisions causes a substantial increase of ion temperature. Coulomb collisions have negligible effect on ion temperature in the pre-sheath, while in the sheath they cause a small cooling of ions. The increase of ɛ causes the increase of ion temperature. From the ion density and temperature profiles, the polytropic function κ is calculated according to its definition given by Kuhn et al. [Phys. Plasmas 13, 013503 (2006)]. The obtained profiles of κ indicate that the ion flow is isothermal only in a relatively narrow region in the pre-sheath, while close to the sheath edge and in the sheath it is closer to adiabatic. The ion sound velocity is space dependent and exhibits a maximum. This maximum indicates the location of the sheath edge only in the limit ɛ → 0 .

Progress at the TITAN-EBIT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klawitter, R.; Alanssari, M.; Frekers, D.

2015-01-09

Precision mass measurements of short-lived isotopes provide insight into a wide array of physics, including nuclear structure, nucleosynthesis, and tests of the Standard Model. The precision of Penning trap mass spectrometry (PTMS) measurements is limited by the lifetime of the isotopes of interest, but scales proportionally with their charge state q, making highly charged ions attractive for mass measurements of nuclides far from stability. TITAN, TRIUMF's Ion Trap(s) for Atomic and Nuclear science, is currently the only setup in the world coupling an EBIT to a rare isotope facility for the purpose of PTMS. Charge breeding ions for Penning trapmore » mass spectrometry, however, entails specific set of challenges. To make use of its potential, efficiencies have to be high, breeding times have to be short and the ion energy spread has to be small. An overview of the TITAN facility and charge-breeding program is given, current and future developments are highlighted and some selected results are presented.« less

Ion and aerosol precursor densities in Titan's ionosphere: A multi-instrument case study

NASA Astrophysics Data System (ADS)

Shebanits, O.; Wahlund, J.-E.; Edberg, N. J. T.; Crary, F. J.; Wellbrock, A.; Andrews, D. J.; Vigren, E.; Desai, R. T.; Coates, A. J.; Mandt, K. E.; Waite, J. H.

2016-10-01

The importance of the heavy ions and dust grains for the chemistry and aerosol formation in Titan's ionosphere has been well established in the recent years of the Cassini mission. In this study we combine independent in situ plasma (Radio Plasma and Wave Science Langmuir Probe (RPWS/LP)) and particle (Cassini Plasma Science Electron Spectrometer, Cassini Plasma Science Ion Beam Spectrometer, and Ion and Neutral Mass Spectrometer) measurements of Titan's ionosphere for selected flybys (T16, T29, T40, and T56) to produce altitude profiles of mean ion masses including heavy ions and develop a Titan-specific method for detailed analysis of the RPWS/LP measurements (applicable to all flybys) to further constrain ion charge densities and produce the first empirical estimate of the average charge of negative ions and/or dust grains. Our results reveal the presence of an ion-ion (dusty) plasma below 1100 km altitude, with charge densities exceeding the primary ionization peak densities by a factor ≥2 in the terminator and nightside ionosphere (ne/ni ≤ 0.1). We suggest that ion-ion (dusty) plasma may also be present in the dayside ionosphere below 900 km (ne/ni < 0.5 at 1000 km altitude). The average charge of the dust grains (≥1000 amu) is estimated to be between -2.5 and -1.5 elementary charges, increasing toward lower altitudes.

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akishev, Yu. S., E-mail: akishev@triniti.ru; Karal’nik, V. B.; Petryakov, A. V.

2017-02-15

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculatedmore » when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.« less

Resilience of the quantum Rabi model in circuit QED

NASA Astrophysics Data System (ADS)

E Manucharyan, Vladimir; Baksic, Alexandre; Ciuti, Cristiano

2017-07-01

In circuit quantum electrodynamics (circuit QED), an artificial ‘circuit atom’ can couple to a quantized microwave radiation much stronger than its real atomic counterpart. The celebrated quantum Rabi model describes the simplest interaction of a two-level system with a single-mode boson field. When the coupling is large enough, the bare multilevel structure of a realistic circuit atom cannot be ignored even if the circuit is strongly anharmonic. We explored this situation theoretically for flux (fluxonium) and charge (Cooper pair box) type multi-level circuits tuned to their respective flux/charge degeneracy points. We identified which spectral features of the quantum Rabi model survive and which are renormalized for large coupling. Despite significant renormalization of the low-energy spectrum in the fluxonium case, the key quantum Rabi feature—nearly-degenerate vacuum consisting of an atomic state entangled with a multi-photon field—appears in both types of circuits when the coupling is sufficiently large. Like in the quantum Rabi model, for very large couplings the entanglement spectrum is dominated by only two, nearly equal eigenvalues, in spite of the fact that a large number of bare atomic states are actually involved in the atom-resonator ground state. We interpret the emergence of the two-fold degeneracy of the vacuum of both circuits as an environmental suppression of flux/charge tunneling due to their dressing by virtual low-/high-impedance photons in the resonator. For flux tunneling, the dressing is nothing else than the shunting of a Josephson atom with a large capacitance of the resonator. Suppression of charge tunneling is a manifestation of the dynamical Coulomb blockade of transport in tunnel junctions connected to resistive leads.

High brilliance negative ion and neutral beam source

DOEpatents

Compton, Robert N.

1991-01-01

A high brilliance mass selected (Z-selected) negative ion and neutral beam source having good energy resolution. The source is based upon laser resonance ionization of atoms or molecules in a small gaseous medium followed by charge exchange through an alkali oven. The source is capable of producing microampere beams of an extremely wide variety of negative ions, and milliampere beams when operated in the pulsed mode.

A tandem mass spectrometer for crossed-beam irradiation of mass-selected molecular systems by keV atomic ions

NASA Astrophysics Data System (ADS)

Schwob, Lucas; Lalande, Mathieu; Chesnel, Jean-Yves; Domaracka, Alicja; Huber, Bernd A.; Maclot, Sylvain; Poully, Jean-Christophe; Rangama, Jimmy; Rousseau, Patrick; Vizcaino, Violaine; Adoui, Lamri; Méry, Alain

2018-04-01

In the present paper, we describe a new home-built crossed-beam apparatus devoted to ion-induced ionization and fragmentation of isolated biologically relevant molecular systems. The biomolecular ions are produced by an electrospray ionization source, mass-over-charge selected, accumulated in a 3D ion trap, and then guided to the extraction region of an orthogonal time-of-flight mass spectrometer. Here, the target molecular ions interact with a keV atomic ion beam produced by an electron cyclotron resonance ion source. Cationic products from the collision are detected on a position sensitive detector and analyzed by time-of-flight mass spectrometry. A detailed description of the operation of the setup is given, and early results from irradiation of a protonated pentapeptide (leucine-enkephalin) by a 7 keV He+ ion beam are presented as a proof-of-principle.

Database and Related Activities in Japan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murakami, Izumi; Kato, Daiji; Kato, Masatoshi

2011-05-11

We have constructed and made available atomic and molecular (AM) numerical databases on collision processes such as electron-impact excitation and ionization, recombination and charge transfer of atoms and molecules relevant for plasma physics, fusion research, astrophysics, applied-science plasma, and other related areas. The retrievable data is freely accessible via the internet. We also work on atomic data evaluation and constructing collisional-radiative models for spectroscopic plasma diagnostics. Recently we have worked on Fe ions and W ions theoretically and experimentally. The atomic data and collisional-radiative models for these ions are examined and applied to laboratory plasmas. A visible M1 transition ofmore » W{sup 26+} ion is identified at 389.41 nm by EBIT experiments and theoretical calculations. We have small non-retrievable databases in addition to our main database. Recently we evaluated photo-absorption cross sections for 9 atoms and 23 molecules and we present them as a new database. We established a new association ''Forum of Atomic and Molecular Data and Their Applications'' to exchange information among AM data producers, data providers and data users in Japan and we hope this will help to encourage AM data activities in Japan.« less

Database and Related Activities in Japan

NASA Astrophysics Data System (ADS)

Murakami, Izumi; Kato, Daiji; Kato, Masatoshi; Sakaue, Hiroyuki A.; Kato, Takako; Ding, Xiaobin; Morita, Shigeru; Kitajima, Masashi; Koike, Fumihiro; Nakamura, Nobuyuki; Sakamoto, Naoki; Sasaki, Akira; Skobelev, Igor; Tsuchida, Hidetsugu; Ulantsev, Artemiy; Watanabe, Tetsuya; Yamamoto, Norimasa

2011-05-01

We have constructed and made available atomic and molecular (AM) numerical databases on collision processes such as electron-impact excitation and ionization, recombination and charge transfer of atoms and molecules relevant for plasma physics, fusion research, astrophysics, applied-science plasma, and other related areas. The retrievable data is freely accessible via the internet. We also work on atomic data evaluation and constructing collisional-radiative models for spectroscopic plasma diagnostics. Recently we have worked on Fe ions and W ions theoretically and experimentally. The atomic data and collisional-radiative models for these ions are examined and applied to laboratory plasmas. A visible M1 transition of W26+ ion is identified at 389.41 nm by EBIT experiments and theoretical calculations. We have small non-retrievable databases in addition to our main database. Recently we evaluated photo-absorption cross sections for 9 atoms and 23 molecules and we present them as a new database. We established a new association "Forum of Atomic and Molecular Data and Their Applications" to exchange information among AM data producers, data providers and data users in Japan and we hope this will help to encourage AM data activities in Japan.

Biased-probe-induced water ion injection into amorphous polymers investigated by electric force microscopy

NASA Astrophysics Data System (ADS)

Knorr, Nikolaus; Rosselli, Silvia; Miteva, Tzenka; Nelles, Gabriele

2009-06-01

Although charging of insulators by atomic force microscopy (AFM) has found widespread interest, often with data storage or nanoxerography in mind, less attention has been paid to the charging mechanism and the nature of the charge. Here we present a systematic study on charging of amorphous polymer films by voltage pulses applied to conducting AFM probes. We find a quadratic space charge limited current law of Kelvin probe force microscopy and electrostatic force microscopy peak volumes in pulse height, offset by a threshold voltage, and a power law in pulse width of positive exponents smaller than one. We interpret the results by a charging mechanism of injection and surface near accumulation of aqueous ions stemming from field induced water adsorption, with threshold voltages linked to the water affinities of the polymers.

High Energy Density Lithium Primary Cells Using Nitrogen Containing Polymer Positives.

DTIC Science & Technology

1983-12-01

the charges were stabilized on heteroatoms, particularly nitro- gen. A positive charge would be stored in the form of an ammonium ion. in a high...operate reversibly. 2.0 POLYMERIC CATHODES A polymer which might be expected to exemplify charge stabilization by nitrogen is poly-N-methylpyrrole (PMP...This material is electronically conductive and might store one charge per nitrogen atom. ox. PMP;4 N3 red. I N + N+ An additional, seductive attraction

Charge exchange, ENAs and the loss of planetary ions at Mars

NASA Astrophysics Data System (ADS)

Kallio, E.; Janhunen, P.; Säles, T.

Neither Mars nor Venus has a strong global intrinsic magnetic field and therefore the solar wind can flow close to the planets in high neutral density regions. Because of the formed direct interaction between the atmosphere/exosphere and the solar wind, the ionized atmospheric neutrals can be picked up by the solar wind. Charge exchange between solar wind protons and planetary neutrals, instead, produce energetic neutral hydrogen atoms (H-ENA) which are the manifestation of the direct interaction between the solar wind and planetary neutrals. Picked-up planetary O+ ions in turn form energetic neutral oxygen atoms (O-ENA) via charge exchange process. The ion escape, H-ENAs, O-ENAs and electrons will be investigated at Mars and Venus by two identical instruments: ASPERA-3 on MarsExpress (measurements started in Jan. 2004) and ASPERA-4 on VenusExpress (2006). We present a self-consistent, three-dimensional quasi-neutral hybrid (ions are particles, electrons a fluid) simulation to study Mars/Venus-solar wind interaction in general and ASPERA-3/4 measurements in particular. Our model includes three ion species (H+, O+, O2+), and contains charge exchange, ion-neutral and chemical reactions. We show results of quasi-neutral hybrid model runs that we have used to study the escape of planetary ions, the effects of planetary ions on the Martian plasma environment and the production and properties of fast hydrogen(H) and oxygen(O) ENAs near Mars. We also compare these hydrogen ENA images with the hydrogen ENA images that has been derived from an empirical flow model by line-of-sight integration. The advantage of the analytical gas dynamic like flow model is that it is computationally so fast that it provides a possibility to perform an ENA inversion, that is, to derive global plasma parameters from the measured ENA image.

Observation of Interspecies Ion Separation in Inertial-Confinement-Fusion Implosions via Imaging X-ray spectroscopy

NASA Astrophysics Data System (ADS)

Joshi, Tirtha Raj

2016-10-01

Interspecies ion separation has been proposed as a yield-degradation mechanism in inertial-confinement-fusion (ICF) experiments. We present direct experimental evidence of interspecies ion separation in direct-drive ICF experiments performed at the OMEGA laser facility. These experiments were designed based on the fact that interspecies ion thermo-diffusion would be strongest for species with large mass and charge difference. The targets were spherical plastic shells filled with D2 and Ar (1% by atom). Ar K-shell spectral features were observed primarily between the time of first-shock convergence and slightly before neutron bang time, using a time- and space-integrated spectrometer, streaked crystal spectrometer, and two gated multi-monochromatic X-ray imagers fielded along quasi-orthogonal lines-of-sight. Detailed spectroscopic analyses of spatially resolved Ar K-shell lines reveal deviation from the initial 1%-Ar gas fill and show both Ar-concentration enhancement and depletion at different times and radial positions of the implosion. The experimental results are interpreted with radiation-hydrodynamic simulations that include recently implemented, first-principles models of interspecies ion diffusion. The experimentally inferred Ar-atom-fraction profiles agree gently with calculated profiles associated with the incoming and rebounding first shock. This work was done in collaboration with P. Hakel, S. C. Hsu, E. L. Vold, M. J. Schmitt, N. M. Hoffman, R. M. Rauenzahn, G. Kagan, X.-Z. Tang, Y. Kim, and H. W. Herrmann of LANL, and R. C. Mancini of UNR. LA-UR-16-24804. Supported by the LANL ICF and ASC Programs under US-DoE contract no. DE-AC52-06NA25396.

Free-bound electron exchange contribution to l-split atomic structure in dense plasmas

NASA Astrophysics Data System (ADS)

Bennadji, K.; Rosmej, F.; Lisitsa, V. S.

2013-11-01

An analytical expression for the exchange energy between the bound electron in hydrogen-like ions and the free electrons of plasma is proposed. Two limiting cases are identified: 1) the low temperature limit where the energy depends linearly on density and on the ion charge as 1/Z2 but does not depend on the temperature itself, 2) the high temperature limit where the energy depends on temperature as 1/T but does not depend on the ion charge. These two regimes are separated by a characteristic temperature (T∗ = 4Z2Ry) which is a universal parameter depending only on the charge Z of the ions. We presented numerical results for aluminum: the exchange energy contributes about 15% to the total plasma energy and can reach an order of 10-4 of the total transition energy. Comparison to the Local-density Approximation (Kohn-Sham) exchange energy shows a good agreement.

Observation of extreme ultraviolet transitions in highly charged Ba{sup 16+} to Ba{sup 23+} ions with electron beam ion trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, S.; Shimizu, E.; Nakamura, N.

2016-03-15

We have investigated extreme ultraviolet emission from highly charged barium using a compact electron beam ion trap at the Tokyo EBIT laboratory. The spectra were recorded for several beam energies ranging from 440 to 740 eV, while keeping the electron beam current constant at 10 mA. Radiation from charge states Zr-like Ba{sup 16+} to As-like Ba{sup 23+} were recorded and identified by varying the electron beam energy across the ionization thresholds and comparing with calculated results. The calculations were performed with a detailed relativistic configuration interaction approach using the Flexible Atomic Code. Several new lines belonging to electric dipole transitions were observedmore » and identified.« less

Isotope shifts from collinear laser spectroscopy of doubly charged yttrium isotopes

NASA Astrophysics Data System (ADS)

Vormawah, L. J.; Vilén, M.; Beerwerth, R.; Campbell, P.; Cheal, B.; Dicker, A.; Eronen, T.; Fritzsche, S.; Geldhof, S.; Jokinen, A.; Kelly, S.; Moore, I. D.; Reponen, M.; Rinta-Antila, S.; Stock, S. O.; Voss, A.

2018-04-01

Collinear laser spectroscopy has been performed on doubly charged ions of radioactive yttrium in order to study the isotope shifts of the 294.6-nm 5 s 1/2 2S →5 p 1/2 2P line. The potential of such an alkali-metal-like transition to improve the reliability of atomic-field-shift and mass-shift factor calculations, and hence the extraction of nuclear mean-square radii, is discussed. Production of yttrium ion beams for such studies is available at the IGISOL IV Accelerator Laboratory, Jyväskylä, Finland. This newly recommissioned facility is described here in relation to the on-line study of accelerator-produced short-lived isotopes using collinear laser spectroscopy and application of the technique to doubly charged ions.

Investigation of the Mechanism of Electron Capture and Electron Transfer Dissociation of Peptides with a Covalently Attached Free Radical Hydrogen Atom Scavenger.

PubMed

Sohn, Chang Ho; Yin, Sheng; Peng, Ivory; Loo, Joseph A; Beauchamp, J L

2015-11-15

The mechanisms of electron capture and electron transfer dissociation (ECD and ETD) are investigated by covalently attaching a free-radical hydrogen atom scavenger to a peptide. The 2,2,6,6-tetramethylpiperidin-l-oxyl (TEMPO) radical was chosen as the scavenger due to its high hydrogen atom affinity (ca. 280 kJ/mol) and low electron affinity (ca. 0.45 ev), and was derivatized to the model peptide, FQX TEMPO EEQQQTEDELQDK. The X TEMPO residue represents a cysteinyl residue derivatized with an acetamido-TEMPO group. The acetamide group without TEMPO was also examined as a control. The gas phase proton affinity (882 kJ/mol) of TEMPO is similar to backbone amide carbonyls (889 kJ/mol), minimizing perturbation to internal solvation and sites of protonation of the derivatized peptides. Collision induced dissociation (CID) of the TEMPO tagged peptide dication generated stable odd-electron b and y type ions without indication of any TEMPO radical induced fragmentation initiated by hydrogen abstraction. The type and abundance of fragment ions observed in the CID spectra of the TEMPO and acetamide tagged peptides are very similar. However, ECD of the TEMPO labeled peptide dication yielded no backbone cleavage. We propose that a labile hydrogen atom in the charge reduced radical ions is scavenged by the TEMPO radical moiety, resulting in inhibition of N-C α backbone cleavage processes. Supplemental activation after electron attachment (ETcaD) and CID of the charge-reduced precursor ion generated by electron transfer of the TEMPO tagged peptide dication produced a series of b + H (b H ) and y + H (y H ) ions along with some c ions having suppressed intensities, consistent with stable O-H bond formation at the TEMPO group. In summary, the results indicate that ECD and ETD backbone cleavage processes are inhibited by scavenging of a labile hydrogen atom by the localized TEMPO radical moiety. This observation supports the conjecture that ECD and ETD processes involve long-lived intermediates formed by electron capture/transfer in which a labile hydrogen atom is present and plays a key role with low energy processes leading to c and z ion formation. Ab initio and density functional calculations are performed to support our conclusion, which depends most importantly on the proton affinity, electron affinity and hydrogen atom affinity of the TEMPO moiety.

Impact parameter sensitive study of inner-shell atomic processes in the experimental storage ring

NASA Astrophysics Data System (ADS)

Gumberidze, A.; Kozhuharov, C.; Zhang, R. T.; Trotsenko, S.; Kozhedub, Y. S.; DuBois, R. D.; Beyer, H. F.; Blumenhagen, K.-H.; Brandau, C.; Bräuning-Demian, A.; Chen, W.; Forstner, O.; Gao, B.; Gassner, T.; Grisenti, R. E.; Hagmann, S.; Hillenbrand, P.-M.; Indelicato, P.; Kumar, A.; Lestinsky, M.; Litvinov, Yu. A.; Petridis, N.; Schury, D.; Spillmann, U.; Trageser, C.; Trassinelli, M.; Tu, X.; Stöhlker, Th.

2017-10-01

In this work, we present a pilot experiment in the experimental storage ring (ESR) at GSI devoted to impact parameter sensitive studies of inner shell atomic processes for low-energy (heavy-) ion-atom collisions. The experiment was performed with bare and He-like xenon ions (Xe54+, Xe52+) colliding with neutral xenon gas atoms, resulting in a symmetric collision system. This choice of the projectile charge states was made in order to compare the effect of a filled K-shell with the empty one. The projectile and target X-rays have been measured at different observation angles for all impact parameters as well as for the impact parameter range of ∼35-70 fm.

The thermally stimulated discharge of ion-irradiated oxide films

NASA Astrophysics Data System (ADS)

Wang, Qiuru; Zeng, Huizhong; Zhang, Wanli

2018-01-01

The ion irradiation technique is utilized to modify the surface structure of amorphous insulating oxide films. While introducing defects, a number of surface charges are injected into the films and captured in the traps during ion irradiation. The variation of surface morphology and the enhancement of emission spectrum corresponding to vacancy defects are respectively verified by atomic force microscopy and photoluminescence measurements. The surface charges trapped in the shallow traps are easy to release caused by thermal excitation, and discharge is observed during heating. Based on the thermally stimulated discharge measurements, the trap parameters of oxide films, such as activation energy and relaxation time, are calculated from experimental data.

Upgrade of the TITAN EBIT High Voltage Operation

NASA Astrophysics Data System (ADS)

Foster, Matt; Titan Collaboration

2016-09-01

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) is a setup dedicated to highly precise mass measurements of short-lived isotopes down to 10ms. TITAN's Electron Beam Ion Trap (EBIT) is a charge breeder integrated into the setup to perform in-trap decay spectroscopy of highly charged ions and increase the precision of mass measurements. In its previous configuration TITAN's EBIT could not fulfil its maximum design specification due to high voltage safety restrictions, limiting its obtainable charge states. A recently completed upgrade of the high voltage operation that will allow the EBIT to fulfil its design specification and achieve higher charge states for heavier species is undergoing preliminary tests with stable beam. Simulations were performed to optimise the injection and extraction efficiency at high voltage and initial tests have involved using a Ge detector to identify x-rays produced by charge breeding stable ions. Future work comprises exploring electron capture rates of Ne-, He- and H-like charge states of 64Cu and higher masses, which were not previously accessible. The function of the EBIT within the TITAN setup, the work carried out on the upgrade thus far and its scope for future work will be presented.

Isobar separation at very low energy for AMS

NASA Astrophysics Data System (ADS)

Litherland, A. E.; Tomski, I.; Zhao, X.-L.; Cousins, Lisa M.; Doupé, J. P.; Javahery, G.; Kieser, W. E.

2007-06-01

The separation of atomic and molecular isobars, prior to injection into a tandem accelerator for Accelerator Mass Spectrometry (AMS), is discussed. To accomplish this separation, the anions from a standard sputter ion source are retarded to eV energy. The advantages of using very low energy (eV) for this purpose are twofold. The ionic reactions in gases can be isobar specific and the multiple scattering of the eV ions, unlike that at higher energy, can be controlled in linear radio-frequency multipoles. An example of current interest to AMS practice, the suppression of the S- isobar ions from negative ion sources generating mainly Cl- ions, will be described. It will be argued that this is a universal method for isobar separation prior to AMS, which is applicable to atomic anions and cations as well as their molecular counterparts. This procedure should be applicable to the AMS analysis of most rare radioactive species, as atomic or molecular ions, starting with either anions or cations, with appropriate charge changing. In some cases the ions may be analysable without AMS.

Summary of initial results from the Magnetized Dusty Plasma Experiment (MDPX) device

NASA Astrophysics Data System (ADS)

Thomas, Edward

2015-11-01

Dusty (or complex) plasmas are four-component plasma systems consisting of electrons, ions, neutral atoms and charged, solid particulates. These particulates, i.e., the ``dust,'' become charged through interactions with the surrounding plasma particles and are therefore fully coupled to the background. The study of dusty plasmas began with astrophysical studies and has developed into a distinct area of plasma science with contributions to industrial, space, and fundamental plasma science. However, the vast majority of the laboratory studies are performed without the presence of a magnetic field. This is because, compared to the masses of the electrons and ions, the dust particles are significantly more massive and therefore the charge-to-mass ratio of the dust is very small. As a result, large (B > 1 T) magnetic fields are required to achieve conditions in which the dynamics of electrons, ions, and dust particles are dominated by the magnetic field. This presentation will provide a brief description of the design of the large bore (50 cm diameter x 158 cm long), multi-configuration, 4-Tesla class, superconducting magnet and integrated plasma chamber optimized for the study of dusty plasmas at high magnetic field - the MDPX device. The presentation will then focus on initial results of measurements made using MDPX - including observations of a new type of imposed ordered structures formed by the dust particles in a magnetized plasma, E x B driven flows of the particles, and observations of instabilities. This work is a collaboration of the author with Uwe Konopka (Auburn), Robert L. Merlino (Univ. of Iowa), Marlene Rosenberg (UCSD), and the MDPX team at Auburn University. Construction of the MDPX device was supported by the NSF-MRI program. Operations are supported by the NSF and DOE.

Genetics Home Reference: CLCN2-related leukoencephalopathy

MedlinePlus

... The CLCN2 gene provides instructions for making a chloride channel called ClC-2. This channel transports negatively charged chlorine atoms (chloride ions) across cell membranes and plays a key ...

Charged Q-ball dark matter from B and L direction

NASA Astrophysics Data System (ADS)

Hong, Jeong-Pyong; Kawasaki, Masahiro; Yamada, Masaki

2016-08-01

We consider nearly equal number of gauge mediation type charged (anti-) Q-balls with charge of ±α-1 simeq ±137 well before the BBN epoch and discussed how they evolve in time. We found that ion-like objects with electric charges of +O(1) are likely to become relics in the present universe, which we expect to be the dark matter. These are constrained by MICA experiment, where the trail of heavy atom-like or ion-like object in 109 years old ancient mica crystals is not observed. We found that the allowed region for gauge mediation model parameter and reheating temperature have to be smaller than the case of the neutral Q-ball dark matter.

Ion species stratification within strong shocks in two-ion plasmas

DOE PAGES

Keenan, Brett D.; Simakov, Andrei N.; Taitano, William T.; ...

2018-03-01

We report strong collisional shocks in multi-ion plasmas are featured in many environments, with Inertial Confinement Fusion (ICF) experiments being one prominent example. Recent work [Keenan et al., Phys. Rev. E 96, 053203 (2017)] answered in detail a number of outstanding questions concerning the kinetic structure of steady-state, planar plasma shocks, e.g., the shock width scaling by the Mach number, M. However, it did not discuss shock-driven ion-species stratification (e.g., relative concentration modification and temperature separation). These are important effects since many recent ICF experiments have evaded explanation by standard, single-fluid, radiation-hydrodynamic (rad-hydro) numerical simulations, and shock-driven fuel stratification likelymore » contributes to this discrepancy. Employing the state-of-the-art Vlasov-Fokker-Planck code, iFP, along with multi-ion hydro simulations and semi-analytics, we quantify the ion stratification by planar shocks with the arbitrary Mach number and the relative species concentration for two-ion plasmas in terms of ion mass and charge ratios. In particular, for strong shocks, we find that the structure of the ion temperature separation has a nearly universal character across ion mass and charge ratios. Lastly, we find that the shock fronts are enriched with the lighter ion species and the enrichment scales as M 4 for M»1.« less

Ion species stratification within strong shocks in two-ion plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keenan, Brett D.; Simakov, Andrei N.; Taitano, William T.

We report strong collisional shocks in multi-ion plasmas are featured in many environments, with Inertial Confinement Fusion (ICF) experiments being one prominent example. Recent work [Keenan et al., Phys. Rev. E 96, 053203 (2017)] answered in detail a number of outstanding questions concerning the kinetic structure of steady-state, planar plasma shocks, e.g., the shock width scaling by the Mach number, M. However, it did not discuss shock-driven ion-species stratification (e.g., relative concentration modification and temperature separation). These are important effects since many recent ICF experiments have evaded explanation by standard, single-fluid, radiation-hydrodynamic (rad-hydro) numerical simulations, and shock-driven fuel stratification likelymore » contributes to this discrepancy. Employing the state-of-the-art Vlasov-Fokker-Planck code, iFP, along with multi-ion hydro simulations and semi-analytics, we quantify the ion stratification by planar shocks with the arbitrary Mach number and the relative species concentration for two-ion plasmas in terms of ion mass and charge ratios. In particular, for strong shocks, we find that the structure of the ion temperature separation has a nearly universal character across ion mass and charge ratios. Lastly, we find that the shock fronts are enriched with the lighter ion species and the enrichment scales as M 4 for M»1.« less

Ion species stratification within strong shocks in two-ion plasmas

NASA Astrophysics Data System (ADS)

Keenan, Brett D.; Simakov, Andrei N.; Taitano, William T.; Chacón, Luis

2018-03-01

Strong collisional shocks in multi-ion plasmas are featured in many environments, with Inertial Confinement Fusion (ICF) experiments being one prominent example. Recent work [Keenan et al., Phys. Rev. E 96, 053203 (2017)] answered in detail a number of outstanding questions concerning the kinetic structure of steady-state, planar plasma shocks, e.g., the shock width scaling by the Mach number, M. However, it did not discuss shock-driven ion-species stratification (e.g., relative concentration modification and temperature separation). These are important effects since many recent ICF experiments have evaded explanation by standard, single-fluid, radiation-hydrodynamic (rad-hydro) numerical simulations, and shock-driven fuel stratification likely contributes to this discrepancy. Employing the state-of-the-art Vlasov-Fokker-Planck code, iFP, along with multi-ion hydro simulations and semi-analytics, we quantify the ion stratification by planar shocks with the arbitrary Mach number and the relative species concentration for two-ion plasmas in terms of ion mass and charge ratios. In particular, for strong shocks, we find that the structure of the ion temperature separation has a nearly universal character across ion mass and charge ratios. Additionally, we find that the shock fronts are enriched with the lighter ion species and the enrichment scales as M4 for M ≫ 1.

Cyclotron transitions of bound ions

NASA Astrophysics Data System (ADS)

Bezchastnov, Victor G.; Pavlov, George G.

2017-06-01

A charged particle in a magnetic field possesses discrete energy levels associated with particle rotation around the field lines. The radiative transitions between these levels are the well-known cyclotron transitions. We show that a bound complex of particles with a nonzero net charge displays analogous transitions between the states of confined motion of the entire complex in the field. The latter bound-ion cyclotron transitions are affected by a coupling between the collective and internal motions of the complex and, as a result, differ from the transitions of a "reference" bare ion with the same mass and charge. We analyze the cyclotron transitions for complex ions by including the coupling within a rigorous quantum approach. Particular attention is paid to comparison of the transition energies and oscillator strengths to those of the bare ion. Selection rules based on integrals of collective motion are derived for the bound-ion cyclotron transitions analytically, and the perturbation and coupled-channel approaches are developed to study the transitions quantitatively. Representative examples are considered and discussed for positive and negative atomic and cluster ions.

Effects of Concentration on Like-Charge Pairing of Guanidinium Ions and on the Structure of Water: An All-Atom Molecular Dynamics Simulation Study.

PubMed

Bandyopadhyay, Dibyendu; Bhanja, K; Mohan, Sadhana; Ghosh, Swapan K; Choudhury, Niharendu

2015-08-27

Like-charge ion-pair formation in an aqueous solution of guanidinium chloride (GdmCl) has two important facets. On one hand, it describes the role of the arginine (ARG) side chain in aggregation and dimer formation in proteins, and on the other hand, it lends support for the direct mechanism of protein denaturation by GdmCl. We employ all-atom molecular dynamics simulations to investigate the effect of GdmCl concentration on the like-charge ion-pair formation of guanidinium ions (Gdm(+)). From analyses of the radial distribution function (RDF) between the carbon atoms of two guanidinium moieties, the existence of both contact pairs and solvent-separated pairs has been observed. Although the peak height corresponding to the contact-pair state decreases, the number of Gdm(+) ions in the contact-pair state actually increases with increasing GdmCl concentration. We have also investigated the effect of the concentration of Gdm(+) on the structure of water. The effect of GdmCl concentration on the radial and tetrahedral structures of water is found to be negligibly small; however, GdmCl concentration has a considerable effect on the hydrogen-bonding structure of water. It is demonstrated that the presence of chloride ions, not Gdm(+), in the first solvation shell of water causes the distortion in the hydrogen-bonding network of water. In order to establish that Gdm(+) not only stacks against another Gdm(+) but also directly attacks the ARG residue of a protein or peptide, simulation of an ARG-rich peptide in 6 M aqueous solution of GdmCl has been performed. The analyses of RDFs and orientation distributions reveal that the Gdm(+) moiety of the GdmCl attacks the same moiety in the ARG side chain with a parallel stacking orientation.

Laboratory Data for X-Ray Astronomy

NASA Technical Reports Server (NTRS)

Beiersdorfer, P.; Brown, G. V.; Chen, H.; Gu, M.-F.; Kahn, S. M.; Lepson, J. K.; Savin, D. W.; Utter, S. B.

2000-01-01

Laboratory facilities have made great strides in producing large sets of reliable data for X-ray astronomy, which include ionization and recombination cross sections needed for charge balance calculations as well as the atomic data needed for interpreting X-ray line formation. We discuss data from the new generation sources and pay special attention to the LLNL electron beam ion trap experiment, which is unique in its ability to provide direct laboratory access to spectral data under precisely controlled conditions that simulate those found in many astrophysical plasmas. Examples of spectral data obtained in the 1-160 A wavelength range are given illustrating the type of laboratory X-ray data produced in support of such missions as Chandra, X-Ray Multi-Mirror telescope (XMM), Advanced Satellite for Cosmology and Astrophysics (ASCA) and Extreme Ultraviolet Explorer Satellite (EUVE).

Energy & mass-charge distribution peculiarities of ion emitted from penning source

NASA Astrophysics Data System (ADS)

Mamedov, N. V.; Kolodko, D. V.; Sorokin, I. A.; Kanshin, I. A.; Sinelnikov, D. N.

2017-05-01

The optimization of hydrogen Penning sources used, in particular, in plasma chemical processing of materials and DLC deposition, is still very important. Investigations of mass-charge composition of these ion source emitted beams are particular relevant for miniature linear accelerators (neutron flux generators) nowadays. The Penning ion source energy and mass-charge ion distributions are presented. The relation between the discharge current abrupt jumps with increasing plasma density in the discharge center and increasing potential whipping (up to 50% of the anode voltage) is shown. Also the energy spectra in the discharge different modes as the pressure and anode potential functions are presented. It has been revealed that the atomic hydrogen ion concentration is about 5-10%, and it weakly depends on the pressure and the discharge current (in the investigated range from 1 to 10 mTorr and from 50 to 1000 μA) and increases with the anode voltage (up 1 to 3,5 kV).

Atomic partial charges on CH{sub 3}NH{sub 3}PbI{sub 3} from first-principles electronic structure calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madjet, Mohamed E., E-mail: mmadjet@qf.org.qa; El-Mellouhi, Fedwa; Carignano, Marcelo A.

We calculated the partial charges in methylammonium (MA) lead-iodide perovskite CH{sub 3}NH{sub 3}PbI{sub 3} in its different crystalline phases using different first-principles electronic charge partitioning approaches, including the Bader, ChelpG, and density-derived electrostatic and chemical (DDEC) schemes. Among the three charge partitioning methods, the DDEC approach provides chemically intuitive and reliable atomic charges for this material, which consists of a mixture of transition metals, halide ions, and organic molecules. The DDEC charges are also found to be robust against the use of hybrid functionals and/or upon inclusion of spin–orbit coupling or dispersive interactions. We calculated explicitly the atomic charges withmore » a special focus on the dipole moment of the MA molecules within the perovskite structure. The value of the dipole moment of the MA is reduced with respect to the isolated molecule due to charge redistribution involving the inorganic cage. DDEC charges and dipole moment of the organic part remain nearly unchanged upon its rotation within the octahedral cavities. Our findings will be of both fundamental and practical importance, as the accurate and consistent determination of the atomic charges is important in order to understand the average equilibrium distribution of the electrons and to help in the development of force fields for larger scale atomistic simulations to describe static, dynamic, and thermodynamic properties of the material.« less

Development of a compact filament-discharge multi-cusp H- ion source.

PubMed

Jia, XianLu; Zhang, TianJue; Zheng, Xia; Qin, JiuChang

2012-02-01

A 14 MeV medical cyclotron with the external ion source has been designed and is being constructed at China Institute of Atomic Energy. The H(-) ion will be accelerated by this machine and the proton beam will be extracted by carbon strippers in dual opposite direction. The compact multi-cusp H(-) ion source has been developed for the cyclotron. The 79.5 mm long ion source is 48 mm in diameter, which is consisting of a special shape filament, ten columns of permanent magnets providing a multi-cusp field, and a three-electrode extraction system. So far, the 3 mA∕25 keV H(-) beam with an emittance of 0.3 π mm mrad has been obtained from the ion source. The paper gives the design details and the beam test results. Further experimental study is under way and an extracted beam of 5 mA is expected.

Carbon-, sulfur-, and phosphorus-based charge transfer reactions in inductively coupled plasma-atomic emission spectrometry

NASA Astrophysics Data System (ADS)

Grindlay, Guillermo; Gras, Luis; Mora, Juan; de Loos-Vollebregt, Margaretha T. C.

2016-01-01

In this work, the influence of carbon-, sulfur-, and phosphorus-based charge transfer reactions on the emission signal of 34 elements (Ag, Al, As, Au, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, I, In, Ir, K, Li, Mg, Mn, Na, Ni, P, Pb, Pd, Pt, S, Sb, Se, Sr, Te, and Zn) in axially viewed inductively coupled plasma-atomic emission spectrometry has been investigated. To this end, atomic and ionic emission signals for diluted glycerol, sulfuric acid, and phosphoric acid solutions were registered and results were compared to those obtained for a 1% w w- 1 nitric acid solution. Experimental results show that the emission intensities of As, Se, and Te atomic lines are enhanced by charge transfer from carbon, sulfur, and phosphorus ions. Iodine and P atomic emission is enhanced by carbon- and sulfur-based charge transfer whereas the Hg atomic emission signal is enhanced only by carbon. Though signal enhancement due to charge transfer reactions is also expected for ionic emission lines of the above-mentioned elements, no experimental evidence has been found with the exception of Hg ionic lines operating carbon solutions. The effect of carbon, sulfur, and phosphorus charge transfer reactions on atomic emission depends on (i) wavelength characteristics. In general, signal enhancement is more pronounced for electronic transitions involving the highest upper energy levels; (ii) plasma experimental conditions. The use of robust conditions (i.e. high r.f. power and lower nebulizer gas flow rates) improves carbon, sulfur, and phosphorus ionization in the plasma and, hence, signal enhancement; and (iii) the presence of other concomitants (e.g. K or Ca). Easily ionizable elements reduce ionization in the plasma and consequently reduce signal enhancement due to charge transfer reactions.

Evidence for strong Breit interaction in dielectronic recombination of highly charged heavy ions.

PubMed

Nakamura, Nobuyuki; Kavanagh, Anthony P; Watanabe, Hirofumi; Sakaue, Hiroyuki A; Li, Yueming; Kato, Daiji; Currell, Fred J; Ohtani, Shunsuke

2008-02-22

Resonant strengths have been measured for dielectronic recombination of Li-like iodine, holmium, and bismuth using an electron beam ion trap. By observing the atomic number dependence of the state-resolved resonant strength, clear experimental evidence has been obtained that the importance of the generalized Breit interaction (GBI) effect on dielectronic recombination increases as the atomic number increases. In particular, it has been shown that the GBI effect is exceptionally strong for the recombination through the resonant state [1s2s(2)2p(1/2)](1).

A table of polyatomic interferences in ICP-MS

USGS Publications Warehouse

May, Thomas W.; Wiedmeyer, Ray H.

1998-01-01

Spectroscopic interferences are probably the largest class of interferences in ICP-MS and are caused by atomic or molecular ions that have the same mass-to-charge as analytes of interest. Current ICP-MS instrumental software corrects for all known atomic “isobaric” interferences, or those caused by overlapping isotopes of different elements, but does not correct for most polyatomic interferences. Such interferences are caused by polyatomic ions that are formed from precursors having numerous sources, such as the sample matrix, reagents used for preparation, plasma gases, and entrained atmospheric gases.

The structure of a magnetic-field front propagating non-diffusively in low-resistivity multi-species plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubinstein, B.; Doron, R., E-mail: ramy.doron@weizmann.ac.il; Maron, Y.

2016-04-15

We report on the first experimental verification of the traveling-wave-like picture of a magnetic-field and an associated electric potential hill propagating non-diffusively in low resistivity plasma. High spatial resolution spectroscopic method, developed here, allowed for obtaining the detailed shape of the propagating magnetic-field front. The measurements demonstrated that the ion separation, previously claimed, results from the reflection of the higher charge-to-mass ratio ions from the propagating potential hill and from climbing the hill by the lower charge-to-mass ratio ions. This ion dynamics is found to be consistent with the observed electron density evolution.

Spectral and Atomic Physics Analysis of Xenon L-Shell Emission From High Energy Laser Produced Plasmas

NASA Astrophysics Data System (ADS)

Thorn, Daniel; Kemp, G. E.; Widmann, K.; Benjamin, R. D.; May, M. J.; Colvin, J. D.; Barrios, M. A.; Fournier, K. B.; Liedahl, D.; Moore, A. S.; Blue, B. E.

2016-10-01

The spectrum of the L-shell (n =2) radiation in mid to high-Z ions is useful for probing plasma conditions in the multi-keV temperature range. Xenon in particular with its L-shell radiation centered around 4.5 keV is copiously produced from plasmas with electron temperatures in the 5-10 keV range. We report on a series of time-resolved L-shell Xe spectra measured with the NIF X-ray Spectrometer (NXS) in high-energy long-pulse (>10 ns) laser produced plasmas at the National Ignition Facility. The resolving power of the NXS is sufficiently high (E/ ∂E >100) in the 4-5 keV spectral band that the emission from different charge states is observed. An analysis of the time resolved L-shell spectrum of Xe is presented along with spectral modeling by detailed radiation transport and atomic physics from the SCRAM code and comparison with predictions from HYDRA a radiation-hydrodynamics code with inline atomic-physics from CRETIN. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

Surface conversion techniques for low energy neutral atom imagers

NASA Technical Reports Server (NTRS)

Quinn, J. M.

1995-01-01

This investigation has focused on development of key technology elements for low energy neutral atom imaging. More specifically, we have investigated the conversion of low energy neutral atoms to negatively charged ions upon reflection from specially prepared surfaces. This 'surface conversion' technique appears to offer a unique capability of detecting, and thus imaging, neutral atoms at energies of 0.01 - 1 keV with high enough efficiencies to make practical its application to low energy neutral atom imaging in space. Such imaging offers the opportunity to obtain the first instantaneous global maps of macroscopic plasma features and their temporal variation. Through previous in situ plasma measurements, we have a statistical picture of large scale morphology and local measurements of dynamic processes. However, with in situ techniques it is impossible to characterize or understand many of the global plasma transport and energization processes. A series of global plasma images would greatly advance our understanding of these processes and would provide the context for interpreting previous and future in situ measurements. Fast neutral atoms, created from ions that are neutralized in collisions with exospheric neutrals, offer the means for remotely imaging plasma populations. Energy and mass analysis of these neutrals provides critical information about the source plasma distribution. The flux of neutral atoms available for imaging depends upon a convolution of the ambient plasma distribution with the charge exchange cross section for the background neutral population. Some of the highest signals are at relatively low energies (well below 1 keV). This energy range also includes some of the most important plasma populations to be imaged, for example the base of the cleft ion fountain.

Optical, structural, and chemical properties of CR-39 implanted with 5.2 MeV doubly charged carbon ions

NASA Astrophysics Data System (ADS)

Ali, Dilawar; Butt, M. Z.; Ishtiaq, Mohsin; Waqas Khaliq, M.; Bashir, Farooq

2016-11-01

Poly-allyl-diglycol-carbonate (CR-39) specimens were irradiated with 5.2 MeV doubly charged carbon ions using Pelletron accelerator. Ion dose was varied from 5 × 1013 to 5 × 1015 ions cm-2. Optical, structural, and chemical properties were investigated by UV-vis spectroscopy, x-ray diffractometer, and FTIR/Raman spectroscopy, respectively. It was found that optical absorption increases with increasing ion dose. Absorption edge shifts from UV region to visible region. The measured opacity values of pristine and ion implanted CR-39 range from 0.0519 to 4.7959 mm-1 following an exponential growth (9141%) with the increase in ion dose. The values of direct and indirect band gap energy decrease exponentially with an increase in ion dose by 59% and 71%, respectively. However, average refractive index in the visible region increases from 1.443 to 2.864 with an increase in ion dose, by 98%. A linear relation between band gap energy and crystallite size was observed. Both the number of carbon atoms in conjugation length and the number of carbon atoms per cluster increase linearly with the increase in ion dose. FTIR spectra showed that on C+2 ions irradiation, the intensity of all bands decreases gradually without appearance of any new band, indicating degradation of polymer after irradiation. Raman spectra revealed that the density of -CH2- group decreases on C+2 ions irradiation. However, the structure of CR-39 is completely destroyed on irradiation with ion dose 1 × 1015 and 5 × 1015 ions cm-2.

Charge-screening role of c -axis atomic displacements in YBa 2 Cu 3 O 6 + x and related superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Božin, E. S.; Huq, A.; Shen, Bing

2016-02-01

The importance of charge reservoir layers for supplying holes to the CuO 2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers. We address this issue in the case of YBa 2 Cu 3 O 6 + x , where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this modelmore » to the temperature-dependent shifts of ions along the c axis, we infer a charge transfer of 5–10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c -axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. This line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi 2 Sr 2 CaCu 2 O 8 + δ .« less

Charge-screening role of c -axis atomic displacements in YBa 2 Cu 3 O 6 + x and related superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Božin, E. S.; Huq, A.; Shen, Bing

2016-02-01

The importance of charge reservoir layers for supplying holes to the CuO2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers.We address this issue in the case of YBa2Cu3O6+x , where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this model to the temperature-dependent shifts of ions along the cmore » axis, we infer a charge transfer of 5–10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c-axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. This line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi2Sr2CaCu2O8+δ .« less

Charge-screening role of c-axis atomic displacements in YBa 2Cu 3O 6+x and related superconductors

DOE PAGES

E. S. Bozin; Huq, A.; Shen, Bing; ...

2016-02-29

The importance of charge reservoir layers for supplying holes to the CuO 2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers. We address this issue in the case of YBa 2Cu 3O 6+x, where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this model to the temperature-dependent shifts ofmore » ions along the c axis, we infer a charge transfer of 5-10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c-axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. Furthermore, this line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi 2Sr 2CaCu 2O 8+δ.« less

Charge states of ions, and mechanisms of charge ordering transitions

NASA Astrophysics Data System (ADS)

Pickett, Warren E.; Quan, Yundi; Pardo, Victor

2014-07-01

To gain insight into the mechanism of charge ordering transitions, which conventionally are pictured as a disproportionation of an ion M as 2Mn+→M(n+1)+ + M(n-1)+, we (1) review and reconsider the charge state (or oxidation number) picture itself, (2) introduce new results for the putative charge ordering compound AgNiO2 and the dual charge state insulator AgO, and (3) analyze the cationic occupations of the actual (not formal) charge, and work to reconcile the conundrums that arise. We establish that several of the clearest cases of charge ordering transitions involve no disproportion (no charge transfer between the cations, and hence no charge ordering), and that the experimental data used to support charge ordering can be accounted for within density functional-based calculations that contain no charge transfer between cations. We propose that the charge state picture retains meaning and importance, at least in many cases, if one focuses on Wannier functions rather than atomic orbitals. The challenge of modeling charge ordering transitions with model Hamiltonians isdiscussed.

Small, pale blue dot' wins photography competition

NASA Astrophysics Data System (ADS)

Banks, Michael

2018-03-01

An image of a single positively charged strontium atom held in an ion trap by electric fields has won a UK science photography competition organized by the Engineering and Physical Sciences Research Council (EPSRC).

Scaling of plasma-body interactions in low Earth orbit

NASA Astrophysics Data System (ADS)

Capon, C. J.; Brown, M.; Boyce, R. R.

2017-04-01

This paper derives the generalised set of dimensionless parameters that scale the interaction of an unmagnetised multi-species plasma with an arbitrarily charged object - the application in this work being to the interaction of the ionosphere with Low Earth Orbiting (LEO) objects. We find that a plasma with K ion species can be described by 1 + 4 K independent dimensionless parameters. These parameters govern the deflection and coupling of ion species k , the relative electrical shielding of the body, electron energy, and scaling of temporal effects. The general shielding length λ ϕ is introduced, which reduces to the Debye length in the high-temperature (weakly coupled) limit. The ability of the scaling parameters to predict the self-similar transformations of single and multi-species plasma interactions is demonstrated numerically using pdFOAM, an electrostatic Particle-in-Cell—Direct Simulation Monte Carlo code. The presented scaling relationships represent a significant generalisation of past work, linking low and high voltage plasma phenomena. Further, the presented parameters capture the scaling of multi-species plasmas with multiply charged ions, demonstrating previously unreported scaling relationship transformations. The implications of this work are not limited to LEO plasma-body interactions but apply to processes governed by the Vlasov-Maxwell equations and represent a framework upon which to incorporate the scaling of additional phenomena, e.g., magnetism and charging.

Hydrodynamic flow of ions and atoms in partially ionized plasmas.

PubMed

Nemirovsky, R A; Fredkin, D R; Ron, A

2002-12-01

We have derived the hydrodynamic equations of motion for a partially ionized plasma, when the ionized component and the neutral components have different flow velocities and kinetic temperatures. Starting from the kinetic equations for a gas of ions and a gas of atoms we have considered various processes of encounters between the two species: self-collisions, interspecies collisions, ionization, recombination, and charge exchange. Our results were obtained by developing a general approach for the hydrodynamics of a gas in a binary mixture, in particular when the components drift with respect to each other. This was applied to a partially ionized plasma, when the neutral-species gas and the charged-species gas have separate velocities. We have further suggested a generalized version of the relaxation time approximation and obtained the contributions of the interspecies encounters to the transport equations.

Detailed Investigations of Interactions between Ionizing Radiation and Neutral Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landers, Allen L

We are investigating phenomena that stem from the many body dynamics associated with ionization of an atom or molecule by photon or charged particle. Our program is funded through the Department of Energy EPSCoR Laboratory Partnership Award in collaboration with Lawrence Berkeley National Laboratory. We are using variations on the well established COLTRIMS technique to measure ions and electrons ejected during these interactions. Photoionization measurements take place at the Advanced Light Source at LBNL as part of the ALS-COLTRIMS collaboration with the groups of Reinhard Dörner at Frankfurt and Ali Belkacem at LBNL. Additional experiments on charged particle impact aremore » conducted locally at Auburn University where we are studying the dissociative molecular dynamics following interactions with either ions or electrons over a velocity range of 1 to 12 atomic units.« less

An assessment for the erosion rate of DEMO first wall

NASA Astrophysics Data System (ADS)

Tokar, M. Z.

2018-01-01

In a fusion reactor a significant fraction of plasma particles lost from the confined volume will reach the vessel wall. The recombination of these charged species, electrons and ions of hydrogen isotopes, is a source of neutral molecules and atoms, recycling back into the plasma. Here they participate, in particular, in charge-exchange (c-x) collisions with the plasma ions and, as a result, atoms of high energies with chaotically oriented velocities are generated. A significant fraction of these hot neutrals will hit the wall, leading, as well as the outflowing fuel and impurity ions, to its erosion, limiting the reactor operation time. The rate of the wall erosion in DEMO is assessed by applying a one-dimensional model which takes into account the transport of charged and neutral species across the flux surfaces in the main part of the scrape-off layer, beyond the X-point vicinity and divertor, and by considering the shift of the centers of flux surfaces, their elongation and triangularity. Atoms generated by c-x of recycling neutrals are modeled kinetically to define firmly their energy spectrum, being of particular importance for the erosion assessment. It is demonstrated the erosion rate of the DEMO wall armor of tungsten will have a pronounced ballooning character with a significant maximum of 0.3 mm per full power year at the low field side, decreasing with an increase in the anomalous perpendicular transport in the ‘far’ SOL or the plasma density at the separatrix.

Development of Optical Crystals for High Power and Tunable Visible and Infrared Light Generation

DTIC Science & Technology

2015-02-11

ultra high chemical purity (5N), 95% isotopically enriched 6Li was purified in a multi-stage vacuum distillation process previously reported by...enriched 6Li was purified in a multi-stage vacuum distillation process previously reported by Stowe et al.[4]. 6LiIn alloy was synthesized in a... quantum mechanics, it has been determined that atoms, molecules, ions have discrete energy levels. Therefore there exists allowed atomic transitions

Accelerated procedure to solve kinetic equation for neutral atoms in a hot plasma

NASA Astrophysics Data System (ADS)

Tokar, Mikhail Z.

2017-12-01

The recombination of plasma charged components, electrons and ions of hydrogen isotopes, on the wall of a fusion reactor is a source of neutral molecules and atoms, recycling back into the plasma volume. Here neutral species participate, in particular, in charge-exchange (c-x) collisions with the plasma ions and, as a result, atoms of high energies with chaotically directed velocities are generated. Some fraction of these hot atoms hit the wall. Statistical Monte Carlo methods normally used to model c-x atoms are too time consuming for reasonably small level of accident errors and extensive parameter studies are problematic. By applying pass method to evaluate integrals from functions, including the ion velocity distribution, an iteration approach to solve one-dimensional kinetic equation [1], being alternative to Monte Carlo procedure, has been tremendously accelerated, at least by a factor of 30-50 [2]. Here this approach is developed further to solve the 2-D kinetic equation, applied to model the transport of c-x atoms in the vicinity of an opening in the wall, e.g., the entrance of the duct guiding to a diagnostic installation. This is necessary to determine firmly the energy spectrum of c-x atoms penetrating into the duct and to assess the erosion of the installation there. The results of kinetic modeling are compared with those obtained with the diffusion description for c-x atoms, being strictly relevant under plasma conditions of low temperature and high density, where the mean free path length between c-x collisions is much smaller than that till the atom ionization by electrons. It is demonstrated that the previous calculations [3], done with the diffusion approximation for c-x atoms, overestimate the erosion rate of Mo mirrors in a reactor by a factor of 3 compared to the result of the present kinetic study.

Vibrational analysis and Y-aromaticity in bis (N,N‧-diphenyl guanidinium) oxalate crystal: A DFT study

NASA Astrophysics Data System (ADS)

Binoy, J.; James, C.; Hubert Joe, I.; Jayakumar, V. S.

2006-02-01

The compound of therapeutic interest, Bis ( N, N'-diphenyl guanidinium) oxalate, have been crystallized and is subjected to FT IR and Raman spectral studies, along with quantum chemical computations using density functional theory. In the crystal, diphenyl guanidinium ion is found to possess anti anti conformation although syn syn conformer is energetically favored based on the single point energy calculations at B3LYP/6-31G(d) level, which shows the counter ion influence on conformation. The optimized geometry at the same level of theory indicates that guanidinium moiety of diphenyl guanidinium ion is planar, possibly induced by the sp 2 hybridized central carbon atom and the twisting of phenyl ring with respect to guanidinium moiety has been observed. The charge delocalization of the planar oxalate ion predicted by XRD is confirmed by the DFT values of bond lengths. The presence of N-H⋯O intermolecular interactions can be observed in IR spectrum by the broadness of the band in the stretching region and its vibrational spectral consequences can be found as the shifting of band positions for amino group and CO group vibrations. The geometry, vibrational spectra, covalent bond orders and atomic charges of guanidinium ion, diphenyl guanidinium ion and of their corresponding neutral species have been used to investigate the effects of charge delocalization leading to Y-aromaticity. The FT IR and Raman spectra of diphenyl guanidine indicates that phenyl ring modes 8b, 18a, 9b and 6b, active in diphenyl guanidine molecule, are found to be dormant in their ionic species.

Tracking dissociation dynamics of strong-field ionized 1,2-dibromoethane with femtosecond XUV transient absorption spectroscopy.

PubMed

Chatterley, Adam S; Lackner, Florian; Neumark, Daniel M; Leone, Stephen R; Gessner, Oliver

2016-06-07

Using femtosecond time-resolved extreme ultraviolet absorption spectroscopy, the dissociation dynamics of the haloalkane 1,2-dibromoethane (DBE) have been explored following strong field ionization by femtosecond near infrared pulses at intensities between 7.5 × 10(13) and 2.2 × 10(14) W cm(-2). The major elimination products are bromine atoms in charge states of 0, +1, and +2. The charge state distribution is strongly dependent on the incident NIR intensity. While the yield of neutral fragments is essentially constant for all measurements, charged fragment yields grow rapidly with increasing NIR intensities with the most pronounced effect observed for Br(++). However, the appearance times of all bromine fragments are independent of the incident field strength; these are found to be 320 fs, 70 fs, and 30 fs for Br˙, Br(+), and Br(++), respectively. Transient molecular ion features assigned to DBE(+) and DBE(++) are observed, with dynamics linked to the production of Br(+) products. Neutral Br˙ atoms are produced on a timescale consistent with dissociation of DBE(+) ions on a shallow potential energy surface. The appearance of Br(+) ions by dissociative ionization is also seen, as evidenced by the simultaneous decay of a DBE(+) ionic species. Dicationic Br(++) products emerge within the instrument response time, presumably from Coulomb explosion of triply charged DBE.

Tracking dissociation dynamics of strong-field ionized 1,2-dibromoethane with femtosecond XUV transient absorption spectroscopy

DOE PAGES

Chatterley, Adam S.; Lackner, Florian; Neumark, Daniel M.; ...

2016-05-11

Using femtosecond time-resolved extreme ultraviolet absorption spectroscopy, the dissociation dynamics of the haloalkane 1,2-dibromoethane (DBE) have been explored following strong field ionization by femtosecond near infrared pulses at intensities between 7.5 × 10 13 and 2.2 × 10 14 W cm -2. The major elimination products are bromine atoms in charge states of 0, +1, and +2. The charge state distribution is strongly dependent on the incident NIR intensity. While the yield of neutral fragments is essentially constant for all measurements, charged fragment yields grow rapidly with increasing NIR intensities with the most pronounced effect observed for Br ++. However,more » the appearance times of all bromine fragments are independent of the incident field strength; these are found to be 320 fs, 70 fs, and 30 fs for Br˙, Br +, and Br ++, respectively. Transient molecular ion features assigned to DBE + and DBE ++ are observed, with dynamics linked to the production of Br + products. Neutral Br˙ atoms are produced on a timescale consistent with dissociation of DBE + ions on a shallow potential energy surface. The appearance of Br + ions by dissociative ionization is also seen, as evidenced by the simultaneous decay of a DBE + ionic species. Dicationic Br ++ products emerge within the instrument response time, presumably from Coulomb explosion of triply charged DBE.« less

Energetic ion bombardment of Ag surfaces by C60+ and Ga+ projectiles.

PubMed

Sun, Shixin; Szakal, Christopher; Winograd, Nicholas; Wucher, Andreas

2005-10-01

The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C60+ cluster projectiles compared with Ga+ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C60+ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga+ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. The experimental findings are in reasonable agreement with recent molecular dynamics simulations.

Interaction of excited He and Ne rare gas metastable atoms with the CHF2Cl molecule

NASA Astrophysics Data System (ADS)

Chérid, M.; Ben Arfa, M.; Driss Khodja, M.

2005-06-01

We studied the Penning ionization of the CHF2Cl molecule with He and Ne metastable atoms (He* and Ne*). We measured the electron kinetic energy and the time-of-flight mass spectra; we also determined the branching ratio for the parent ion and charged CHF+2, CHFCl+, HCF+/CF+ and Cl+ fragments. These data led us to discuss the dissociation channels for all the energetically-accessible electronic states of the ionized molecule. We evidenced a marked contrast in the fragment ion proportions for Ne*-CHF2Cl and He*-CHF2Cl systems, and related it to the difference in polarizability and internal energy of the He* and Ne* atoms.

Refined Dummy Atom Model of Mg(2+) by Simple Parameter Screening Strategy with Revised Experimental Solvation Free Energy.

PubMed

Jiang, Yang; Zhang, Haiyang; Feng, Wei; Tan, Tianwei

2015-12-28

Metal ions play an important role in the catalysis of metalloenzymes. To investigate metalloenzymes via molecular modeling, a set of accurate force field parameters for metal ions is highly imperative. To extend its application range and improve the performance, the dummy atom model of metal ions was refined through a simple parameter screening strategy using the Mg(2+) ion as an example. Using the AMBER ff03 force field with the TIP3P model, the refined model accurately reproduced the experimental geometric and thermodynamic properties of Mg(2+). Compared with point charge models and previous dummy atom models, the refined dummy atom model yields an enhanced performance for producing reliable ATP/GTP-Mg(2+)-protein conformations in three metalloenzyme systems with single or double metal centers. Similar to other unbounded models, the refined model failed to reproduce the Mg-Mg distance and favored a monodentate binding of carboxylate groups, and these drawbacks needed to be considered with care. The outperformance of the refined model is mainly attributed to the use of a revised (more accurate) experimental solvation free energy and a suitable free energy correction protocol. This work provides a parameter screening strategy that can be readily applied to refine the dummy atom models for metal ions.

Design study of low-energy beam transport for multi-charge beams at RAON

NASA Astrophysics Data System (ADS)

Bahng, Jungbae; Qiang, Ji; Kim, Eun-San

2015-12-01

The Rare isotope Accelerator Of Newness (RAON) at the Rare Isotope Science Project (RISP) is being designed to simultaneously accelerate beams with multiple charge states. It includes a driver superconducting (SC) linac for producing 200 MeV/u and 400 kW continuous wave (CW) heavy ion beams from protons to uranium. The RAON consists of a few electron cyclotron resonance ion sources, a low-energy beam transport (LEBT) system, a CW 81.25 MHz, 500 keV/u radio frequency quadrupole (RFQ) accelerator, a medium-energy beam transport system, the SC linac, and a charge-stripper system. The LEBT system for the RISP accelerator facility consists of a high-voltage platform, two 90° dipoles, a multi-harmonic buncher (MHB), solenoids, electrostatic quadrupoles, a velocity equalizer, and a diagnostic system. The ECR ion sources are located on a high-voltage platform to reach an initial beam energy of 10 keV/u. After extraction, the ion beam is transported through the LEBT system to the RFQ accelerator. The generated charge states are selected by an achromatic bending system and then bunched by the MHB in the LEBT system. The MHB is used to achieve a small longitudinal emittance in the RFQ by generating a sawtooth wave with three harmonics. In this paper, we present the results and issues of the beam dynamics of the LEBT system.

Photoluminescence from Au ion-implanted nanoporous single-crystal 12CaO•7Al2O3

NASA Astrophysics Data System (ADS)

Miyakawa, Masashi; Kamioka, Hayato; Hirano, Masahiro; Kamiya, Toshio; Sushko, Peter V.; Shluger, Alexander L.; Matsunami, Noriaki; Hosono, Hideo

2006-05-01

Implantation of Au+ ions into a single crystalline 12CaO•7Al2O3 (C12A7) was performed at high temperatures with fluences from 1×1014 to 3×1016cm-2 . This material is composed of positively charged sub-nanometer-sized cages compensated by extra-framework negatively charged species. The depth profile of concentrations of Au species was analyzed using Rutherford backscattering spectrometry. The measured optical spectra and ab initio embedded cluster calculations show that the implanted Au species are stabilized in the form of negative Au- ions below the fluences of ˜1×1016cm-2 (Au volume concentration of ˜2×1021cm-3 ). These ions are trapped in the cages and exhibit photoluminescence (PL) bands peaking at 3.05 and 2.34eV at temperatures below 150K . At fluences exceeding ˜3×1016cm-2 , the implanted Au atoms form nano-sized clusters. This is manifested in quenching of the PL bands and creation of an optical absorption band at 2.43eV due to the surface plasmon of free carriers in the cluster. The PL bands are attributed to the charge transfer transitions (Au0+e-→Au-) due to recombination of photo-excited electrons (e-) , transiently transferred by ultraviolet excitation into a nearby cages, with Au0 atoms.

Charge Sharing and Charge Loss in a Cadmium-Zinc-Telluride Fine-Pixel Detector Array

NASA Technical Reports Server (NTRS)

Gaskin, J. A.; Sharma, D. P.; Ramsey, B. D.; Six, N. Frank (Technical Monitor)

2002-01-01

Because of its high atomic number, room temperature operation, low noise, and high spatial resolution a Cadmium-Zinc-Telluride (CZT) multi-pixel detector is ideal for hard x-ray astrophysical observation. As part of on-going research at MSFC (Marshall Space Flight Center) to develop multi-pixel CdZnTe detectors for this purpose, we have measured charge sharing and charge loss for a 4x4 (750micron pitch), lmm thick pixel array and modeled these results using a Monte-Carlo simulation. This model was then used to predict the amount of charge sharing for a much finer pixel array (with a 300micron pitch). Future work will enable us to compare the simulated results for the finer array to measured values.

Kinetics of wet sodium vapor complex plasma

NASA Astrophysics Data System (ADS)

Mishra, S. K.; Sodha, M. S.

2014-04-01

In this paper, we have investigated the kinetics of wet (partially condensed) Sodium vapor, which comprises of electrons, ions, neutral atoms, and Sodium droplets (i) in thermal equilibrium and (ii) when irradiated by light. The formulation includes the balance of charge over the droplets, number balance of the plasma constituents, and energy balance of the electrons. In order to evaluate the droplet charge, a phenomenon for de-charging of the droplets, viz., evaporation of positive Sodium ions from the surface has been considered in addition to electron emission and electron/ion accretion. The analysis has been utilized to evaluate the steady state parameters of such complex plasmas (i) in thermal equilibrium and (ii) when irradiated; the results have been graphically illustrated. As a significant outcome irradiated, Sodium droplets are seen to acquire large positive potential, with consequent enhancement in the electron density.

Effective atomic number, energy loss and radiation damage studies in some materials commonly used in nuclear applications for heavy charged particles such as H, C, Mg, Fe, Te, Pb and U

NASA Astrophysics Data System (ADS)

Kurudirek, Murat

2016-05-01

Commonly used nuclear physics materials such as water, concrete, Pb-glass, paraffin, freon and P 10 gases, some alloys such as brass, bronze, stainless-steel and some scintillators such as anthracene, stilbene and toluene have been investigated with respect to the heavy charged particle interaction as means of projected range and effective atomic number (Zeff) in the energy region 10 keV to 10 MeV. Calculations were performed for heavy ions such as H, C, Mg, Fe, Te, Pb and U. Also, the energy loss and radiation damage were studied using SRIM Monte Carlo code for anthracene for different heavy ions of 100 keV kinetic energy. It has been observed that the variation in Zeff becomes less when the atomic number of the ions increase. Glass-Pb, bronze, brass, stainless-steel and Freon gas were found to vary less than 10% in the energy region 10 keV to 10 MeV. For total proton interaction, discrepancies up to 10% and 18% between two databases namely PSTAR and SRIM were noted in mass stopping power and Zeff of water, respectively. The range calculations resulted with a conclusion that the metal alloys and glass-Pb have lowest values of ranges confirming best shielding against energetic heavy ions whereas freon and P 10 gases have the highest values of ranges in the entire energy region. The simulation results showed that the energy loss (%) to target electrons decreases as the Z of the incident ion increases. Also, it was observed that the radiation damage first increases with Z of the ion and then keeps almost constant for ions with Z≥52.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Jeong-Pyong; Kawasaki, Masahiro; Kavli IPMU

We consider nearly equal number of gauge mediation type charged (anti-) Q-balls with charge of ±α{sup −1}≃±137 well before the BBN epoch and discussed how they evolve in time. We found that ion-like objects with electric charges of +O(1) are likely to become relics in the present universe, which we expect to be the dark matter. These are constrained by MICA experiment, where the trail of heavy atom-like or ion-like object in 10{sup 9} years old ancient mica crystals is not observed. We found that the allowed region for gauge mediation model parameter and reheating temperature have to be smallermore » than the case of the neutral Q-ball dark matter.« less

Multi-timescale power and energy assessment of lithium-ion battery and supercapacitor hybrid system using extended Kalman filter

NASA Astrophysics Data System (ADS)

Wang, Yujie; Zhang, Xu; Liu, Chang; Pan, Rui; Chen, Zonghai

2018-06-01

The power capability and maximum charge and discharge energy are key indicators for energy management systems, which can help the energy storage devices work in a suitable area and prevent them from over-charging and over-discharging. In this work, a model based power and energy assessment approach is proposed for the lithium-ion battery and supercapacitor hybrid system. The model framework of the lithium-ion battery and supercapacitor hybrid system is developed based on the equivalent circuit model, and the model parameters are identified by regression method. Explicit analyses of the power capability and maximum charge and discharge energy prediction with multiple constraints are elaborated. Subsequently, the extended Kalman filter is employed for on-board power capability and maximum charge and discharge energy prediction to overcome estimation error caused by system disturbance and sensor noise. The charge and discharge power capability, and the maximum charge and discharge energy are quantitatively assessed under both the dynamic stress test and the urban dynamometer driving schedule. The maximum charge and discharge energy prediction of the lithium-ion battery and supercapacitor hybrid system with different time scales are explored and discussed.

Atoms and Ions; Universality, Singularity and Particularity:. on Boltzmann's Vision a Century Later

NASA Astrophysics Data System (ADS)

Fisher, Michael

2008-12-01

Ludwig Boltzmann died by his own hand 101 years ago last September. He was a passionate believer in atoms: underlying thermodynamics, he felt, lay a statistical world governed by the mechanics of individual particles. His struggles against critics -- "Have you ever seen an atom?" taunted Ernst Mach -- left him pessimistic. Nevertheless, following Maxwell and clarified by Gibbs, he established the science of Statistical Mechanics. But today, especially granted our understanding of critical singularities and their universality, how much do atomic particles and their charged partners, ions, really matter? The answers we have also met opposition. But Boltzmann would have welcomed the insights gained and approved of applications of statistical dynamics to biology, sociology, and other enterprises. Note from Publisher: This article contains the abstract only.

Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franz, Robert; Polcik, Peter; Anders, André

The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al+ regardless of the background gas species, whereas Cr 2+ ions were dominating in Ar and N 2 and Cr + in O 2 atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ionsmore » that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O 2 atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings.« less

Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres

DOE PAGES

Franz, Robert; Polcik, Peter; Anders, André

2015-06-01

The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al+ regardless of the background gas species, whereas Cr 2+ ions were dominating in Ar and N 2 and Cr + in O 2 atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ionsmore » that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O 2 atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings.« less

A gated Thomson parabola spectrometer for improved ion and neutral atom measurements in intense laser produced plasmas

NASA Astrophysics Data System (ADS)

Tata, Sheroy; Mondal, Angana; Sarkar, Soubhik; Lad, Amit D.; Krishnamurthy, M.

2017-08-01

Ions of high energy and high charge are accelerated from compact intense laser produced plasmas and are routinely analysed either by time of flight or Thomson parabola spectrometry. At the highest intensities where ion energies can be substantially large, both these techniques have limitations. Strong electromagnetic pulse noise jeopardises the arrival time measurement, and a bright central spot in the Thomson parabola spectrometer affects the signal to noise ratio of ion traces that approach close to the central spot. We present a gated Thomson parabola spectrometer that addresses these issues and provides an elegant method to improvise ion spectrometry. In addition, we demonstrate that this method provides the ability to detect and measure high energy neutral atoms that are invariably present in most intense laser plasma acceleration experiments.

A gated Thomson parabola spectrometer for improved ion and neutral atom measurements in intense laser produced plasmas.

PubMed

Tata, Sheroy; Mondal, Angana; Sarkar, Soubhik; Lad, Amit D; Krishnamurthy, M

2017-08-01

Ions of high energy and high charge are accelerated from compact intense laser produced plasmas and are routinely analysed either by time of flight or Thomson parabola spectrometry. At the highest intensities where ion energies can be substantially large, both these techniques have limitations. Strong electromagnetic pulse noise jeopardises the arrival time measurement, and a bright central spot in the Thomson parabola spectrometer affects the signal to noise ratio of ion traces that approach close to the central spot. We present a gated Thomson parabola spectrometer that addresses these issues and provides an elegant method to improvise ion spectrometry. In addition, we demonstrate that this method provides the ability to detect and measure high energy neutral atoms that are invariably present in most intense laser plasma acceleration experiments.

Ion guiding accompanied by formation of neutrals in polyethylene terephthalate polymer nanocapillaries: Further insight into a self-organizing process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juhasz, Z.; Sulik, B.; Racz, R.

2010-12-15

A relatively large yield of neutralized atoms was observed when 3 keV Ar{sup 7+} ions were guided trough polyethylene terephthalate nanocapillaries. Time and deposited-charge dependence of the angular distribution of both the guided ions and the neutrals was measured simultaneously using a two-dimensional multichannel plate detector. The yield of neutrals increased significantly faster than that of guided ions and saturated typically at a few percent level. In accordance with earlier observations, both the yield and the mean emission angle of the guided ions exhibited strong oscillations. For the atoms, the equilibrium was achieved not only faster, but also without significantmore » oscillations in yield and angular position. A phase analysis of these time dependencies provides insight into the dynamic features of the self-organizing mechanisms, which leads to ion guiding in insulating nanocapillaries.« less

The TFTR E Parallel B Spectrometer for Mass and Energy Resolved Multi-Ion Charge Exchange Diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

A.L. Roquemore; S.S. Medley

1998-01-01

The Charge Exchange Neutral Analyzer diagnostic for the Tokamak Fusion Test Reactor was designed to measure the energy distributions of both the thermal ions and the supra thermal populations arising from neutral-beam injection and ion cyclotron radio-frequency heating. These measurements yield the plasma ion temperature, as well as several other plasma parameters necessary to provide an understanding of the plasma condition and the performance of the auxiliary heating methods. For this application, a novel charge-exchange spectrometer using a dee-shaped region of parallel electric and magnetic fields was developed at the Princeton Plasma Physics Laboratory. The design and performance of thismore » spectrometer is described in detail, including the effects of exposure of the microchannel plate detector to magnetic fields, neutrons, and tritium.« less

κ -distributed protons in the solar wind and their charge-exchange coupling to energetic hydrogen

DOE PAGES

Heerikhuisen, J.; Zirnstein, Eric; Pogorelov, Nikolai

2015-03-16

The interaction between the solar wind and the interstellar medium represents a collision between two plasma flows, resulting in a heliosphere with an extended tail. While the solar wind is mostly ionized material from the corona, the interstellar medium is only partially ionized. The ion and neutral populations are coupled through charge-exchange collisions that operate on length scales of tens to hundreds of astronomical units. About half the interstellar hydrogen flows into the heliosphere where it may charge-exchange with solar wind protons. This process gives rise to a nonthermal proton, known as a pickup ion, which joins the plasma. Inmore » this paper we investigate the effects of approximating the total ion distribution of the subsonic solar wind as a generalized Lorentzian, or κ distribution, using an MHD neutral code. We illustrate the effect different values of the κ parameter have on both the structure of the heliosphere and the energetic neutral atom flux at 1 AU. We find that using a κ distribution in our simulations yields levels of energetic neutral atom flux that are within a factor of about 2 or 3 over the IBEX-Hi range of energies from 0.5 to 6 keV. In conclusion, while the presence of a suprathermal tail in the proton distribution leads to the production of high-energy neutrals, the sharp decline in the charge-exchange cross section around 10 keV mitigates the enhanced transfer of energy from the ions to the neutrals that might otherwise be expected.« less

Ion-neutral chemistry at ultralow energies: dynamics of reactive collisions between laser-cooled Ca+ ions and Rb atoms in an ion-atom hybrid trap†

NASA Astrophysics Data System (ADS)

Hall, Felix H. J.; Eberle, Pascal; Hegi, Gregor; Raoult, Maurice; Aymar, Mireille; Dulieu, Olivier; Willitsch, Stefan

2013-08-01

Cold chemical reactions between laser-cooled Ca+ ions and Rb atoms were studied in an ion-atom hybrid trap. Reaction rate constants were determined in the range of collision energies ⟨E coll⟩/k B=20 mK-20 K. The lowest energies were achieved in experiments using single localised Ca+ ions. Product branching ratios were studied using resonant-excitation mass spectrometry. The dynamics of the reactive processes in this system (non-radiative and radiative charge transfer as well as radiative association leading to the formation of CaRb+ molecular ions) have been analysed using high-level quantum-chemical calculations of the potential energy curves of CaRb+ and quantum-scattering calculations for the radiative channels. For the present low-energy scattering experiments, it is shown that the energy dependence of the reaction rate constants is governed by long-range interactions in line with the classical Langevin model, but their magnitude is determined by short-range non-adiabatic and radiative couplings which only weakly depend on the asymptotic energy. The quantum character of the collisions is predicted to manifest itself in the occurrence of narrow shape resonances at well-defined collision energies. The present results highlight both universal and system-specific phenomena in cold ion-neutral reactive collisions.

Dielectronic recombination experiments at the storage rings: From the present CSR to the future HIAF

NASA Astrophysics Data System (ADS)

Huang, Z. K.; Wen, W. Q.; Xu, X.; Wang, H. B.; Dou, L. J.; Chuai, X. Y.; Zhu, X. L.; Zhao, D. M.; Li, J.; Ma, X. M.; Mao, L. J.; Yang, J. C.; Yuan, Y. J.; Xu, W. Q.; Xie, L. Y.; Xu, T. H.; Yao, K.; Dong, C. Z.; Zhu, L. F.; Ma, X.

2017-10-01

Dielectronic recombination (DR) experiments of highly charged ions at the storage rings have been developed as a precision spectroscopic tool to investigate the atomic structure as well as nuclear properties of stable and unstable nuclei. The DR experiment on lithium-like argon ions was successfully performed at main Cooler Storage Ring (CSRm) at Heavy Ion Research Facility in Lanzhou (HIRFL) accelerator complex. The DR experiments on heavy highly charged ions and even radioactive ions are currently under preparation at the experimental Cooler Storage Ring (CSRe) at HIRFL. The current status of DR experiments at the CSRm and the preparation of the DR experiments at the CSRe are presented. In addition, an overview of DR experiments by employing an electron cooler and a separated ultra-cold electron target at the upcoming High Intensity heavy ion Accelerator Facility (HIAF) will be given.

Synergetic effects of K + and Mg 2+ ion intercalation on the electrochemical and actuation properties of the two-dimensional Ti 3 C 2 MXene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Qiang; Come, Jeremy; Naguib, Michael

2017-01-01

Two-dimensional materials, such as MXenes, are attractive candidates for energy storage and electrochemical actuators due to their high volume changes upon ion intercalation. Of special interest for boosting energy storage is the intercalation of multivalent ions such as Mg 2+, which suffers from sluggish intercalation and transport kinetics due to its ion size. By combining traditional electrochemical characterization techniques with electrochemical dilatometry and contact resonance atomic force microscopy, the synergetic effects of the pre-intercalation of K +ions are demonstrated to improve the charge storage of multivalent ions, as well as tune the mechanical and actuation properties of the Ti 3Cmore » 2MXene. Our results have important implications for quantitatively understanding the charge storage processes in intercalation compounds and provide a new path for studying the mechanical evolution of energy storage materials.« less

New developments of the in-source spectroscopy method at RILIS/ISOLDE

NASA Astrophysics Data System (ADS)

Marsh, B. A.; Andel, B.; Andreyev, A. N.; Antalic, S.; Atanasov, D.; Barzakh, A. E.; Bastin, B.; Borgmann, Ch.; Capponi, L.; Cocolios, T. E.; Day Goodacre, T.; Dehairs, M.; Derkx, X.; De Witte, H.; Fedorov, D. V.; Fedosseev, V. N.; Focker, G. J.; Fink, D. A.; Flanagan, K. T.; Franchoo, S.; Ghys, L.; Huyse, M.; Imai, N.; Kalaninova, Z.; Köster, U.; Kreim, S.; Kesteloot, N.; Kudryavtsev, Yu.; Lane, J.; Lecesne, N.; Liberati, V.; Lunney, D.; Lynch, K. M.; Manea, V.; Molkanov, P. L.; Nicol, T.; Pauwels, D.; Popescu, L.; Radulov, D.; Rapisarda, E.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Schweikhard, L.; Seliverstov, M. D.; Sels, S.; Sjödin, A. M.; Truesdale, V.; Van Beveren, C.; Van Duppen, P.; Wendt, K.; Wienholtz, F.; Wolf, R. N.; Zemlyanoy, S. G.

2013-12-01

At the CERN ISOLDE facility, long isotope chains of many elements are produced by proton-induced reactions in target materials such as uranium carbide. The Resonance Ionization Laser Ion Source (RILIS) is an efficient and selective means of ionizing the reaction products to produce an ion beam of a chosen isotope. Coupling the RILIS with modern ion detection techniques enables highly sensitive studies of nuclear properties (spins, electromagnetic moments and charge radii) along an isotope chain, provided that the isotope shifts and hyperfine structure splitting of the atomic transitions can be resolved. At ISOLDE the campaign to measure the systematics of isotopes in the lead region (Pb, Bi, Tl and Po) has been extended to include the gold and astatine isotope chains. Several developments were specifically required for the feasibility of the most recent measurements: new ionization schemes (Po, At); a remote controlled narrow line-width mode of operation for the RILIS Ti:sapphire laser (At, Au, Po); isobar free ionization using the Laser Ion Source Trap, LIST (Po); isobar selective particle identification using the multi-reflection time-of-flight mass separator (MR-ToF MS) of ISOLTRAP (Au, At). These are summarized as part of an overview of the current status of the in-source resonance ionization spectroscopy setup at ISOLDE.

Genetics Home Reference: metatropic dysplasia

MedlinePlus

... TRPV4 gene, which provides instructions for making a protein that acts as a calcium channel . The TRPV4 channel transports positively charged calcium atoms (calcium ions) across cell membranes and into cells. The channel is found in ...

Experimental evaluation of analyte excitation mechanisms in the inductively coupled plasma

NASA Astrophysics Data System (ADS)

Lehn, Scott A.; Hieftje, Gary M.

2003-10-01

The inductively coupled plasma (ICP) is a justifiably popular source for atomic emission spectrometry. However, despite its popularity, the ICP is still only partially understood. Even the mechanisms of analyte excitation remain unclear; some energy levels are quite clearly populated by charge transfer while others might be populated by electron-ion recombination, by electron impact, or by Penning processes. Distinguishing among these alternatives is possible by means of a steady-state kinetics approach that examines correlations between the emission of a selected atom, ion, or level and the local number densities of species assumed to produce the excitation. In an earlier investigation, strong correlations were found between either calcium atom or ion emission and selected combinations of calcium atom or ion number densities and electron number densities in the plasma. However, all radially resolved data employed in the earlier study were produced from Abel inversion and from measurements that were crude by today's standards. Now, by means of tomographic imaging, laser-saturated atomic fluorescence, and Thomson and Rayleigh scattering, it is possible to measure the required radially resolved data without Abel inversion and with far greater fidelity. The correlations previously studied for calcium have been investigated with these more reliable data. Ion-electron recombination, either radiative or with argon as a third body, was determined to be the most likely excitation mechanism for calcium atom, while electron impact appeared to be the most important process to produce excite-state calcium ions. These results were consistent with the previous study. However, the present study suggests that collisional deactivation, rather than radiative decay, is the most likely mode of returning both calcium atoms and ions to the ground state.

Ion-ion correlations across and between electrified graphene layers

NASA Astrophysics Data System (ADS)

Mendez-Morales, Trinidad; Burbano, Mario; Haefele, Matthieu; Rotenberg, Benjamin; Salanne, Mathieu

2018-05-01

When an ionic liquid adsorbs onto a porous electrode, its ionic arrangement is deeply modified due to a screening of the Coulombic interactions by the metallic surface and by the confinement imposed upon it by the electrode's morphology. In particular, ions of the same charge can approach at close contact, leading to the formation of a superionic state. The impact of an electrified surface placed between two liquid phases is much less understood. Here we simulate a full supercapacitor made of the 1-butyl-3-methylimidazolium hexafluorophosphate and nanoporous graphene electrodes, with varying distances between the graphene sheets. The electrodes are held at constant potential by allowing the carbon charges to fluctuate. Under strong confinement conditions, we show that ions of the same charge tend to adsorb in front of each other across the graphene plane. These correlations are allowed by the formation of a highly localized image charge on the carbon atoms between the ions. They are suppressed in larger pores, when the liquid adopts a bilayer structure between the graphene sheets. These effects are qualitatively similar to the recent templating effects which have been reported during the growth of nanocrystals on a graphene substrate.

A spectral study of a radio-frequency plasma-generated flux of atomic oxygen

NASA Technical Reports Server (NTRS)

Batten, Carmen E.; Brown, Kenneth G.; Lewis, Beverley W.

1994-01-01

The active environment of a radio-frequency (RF) plasma generator, with and without low-pressure oxygen, has been characterized through the identification of emission lines in the spectral region from 250 to 900 nm. The environment is shown to be dependent on the partial pressure of oxygen and the power applied to the RF generator. Atomic oxygen has been found in significant amounts as well as atomic hydrogen and the molecular oxygen species O2((sup 1)Sigma). The only charged species observed was the singly charged molecular ion O2(+). With a polymer specimen in the plasma chamber, carbon monoxide was also observed. The significance of these observations with respect to previous studies using this type of generator to stimulate material degradation in space is discussed. The possibility of using these generators as atomic oxygen sources in the development of oxygen atom fluorescence sensors is explored.

Multi-photon ionization of atoms in intense short-wavelength radiation fields

NASA Astrophysics Data System (ADS)

Meyer, Michael

2015-05-01

The unprecedented characteristics of XUV and X-ray Free Electron Lasers (FELs) have stimulated numerous investigations focusing on the detailed understanding of fundamental photon-matter interactions in atoms and molecules. In particular, the high intensities (up to 106 W/cm2) giving rise to non-linear phenomena in the short wavelength regime. The basic phenomenology involves the production of highly charged ions via electron emission to which both sequential and direct multi-photon absorption processes contribute. The detailed investigation of the role and relative weight of these processes under different conditions (wavelength, pulse duration, intensity) is the key element for a comprehensive understanding of the ionization dynamics. Here the results of recent investigations are presented, performed at the FELs in Hamburg (FLASH) and Trieste (FERMI) on atomic systems with electronic structures of increasing complexity (Ar, Ne and Xe). Mainly, electron spectroscopy is used to obtain quantitative information about the relevance of various multi-photon ionization processes. For the case of Ar, a variety of processes including above threshold ionization (ATI) from 3p and 3s valence shells, direct 2p two-photon ionization and resonant 2p-4p two-photon excitations were observed and their role was quantitatively determined comparing the experimental ionization yields to ab-initio calculations of the cross sections for the multi-photon processes. Using Ar as a benchmark to prove the reliability of the combined experimental and theoretical approach, the more complex and intriguing case of Xe was studied. Especially, the analysis of the two-photon ATI from the Xe 4d shell reveals new insight into the character of the 4d giant resonance, which was unresolved in the linear one-photon regime. Finally, the influence of intense XUV radiation to the relaxation dynamics of the Ne 2s-3p resonance was investigated by angle-resolved electron spectroscopy, especially be observing the intensity dependent variation of the angular distribution patterns for the sequential ionization process.

Scrape-off layer modeling with kinetic or diffusion description of charge-exchange atoms

NASA Astrophysics Data System (ADS)

Tokar, M. Z.

2016-12-01

Hydrogen isotope atoms, generated by charge-exchange (c-x) of neutral particles recycling from the first wall of a fusion reactor, are described either kinetically or in a diffusion approximation. In a one-dimensional (1-D) geometry, kinetic calculations are accelerated enormously by applying an approximate pass method for the assessment of integrals in the velocity space. This permits to perform an exhaustive comparison of calculations done with both approaches. The diffusion approximation is deduced directly from the velocity distribution function of c-x atoms in the limit of charge-exchanges with ions occurring much more frequently than ionization by electrons. The profiles across the flux surfaces of the plasma parameters averaged along the main part of the scrape-off layer (SOL), beyond the X-point and divertor regions, are calculated from the one-dimensional equations where parallel flows of charged particles and energy towards the divertor are taken into account as additional loss terms. It is demonstrated that the heat losses can be firmly estimated from the SOL averaged parameters only; for the particle loss the conditions in the divertor are of importance and the sensitivity of the results to the so-called "divertor impact factor" is investigated. The coupled 1-D models for neutral and charged species, with c-x atoms described either kinetically or in the diffusion approximation, are applied to assess the SOL conditions in a fusion reactor, with the input parameters from the European DEMO project. It is shown that the diffusion approximation provides practically the same profiles across the flux surfaces for the plasma density, electron, and ion temperatures, as those obtained with the kinetic description for c-x atoms. The main difference between the two approaches is observed in the characteristics of these species themselves. In particular, their energy flux onto the wall is underestimated in calculations with the diffusion approximation by 20 % - 30 % . This discrepancy can be significantly reduced if after the convergence of coupled plasma-neutral calculations, the final computation for c-x atoms is done kinetically.

Energy and charge transfer in ionized argon coated water clusters.

PubMed

Kočišek, J; Lengyel, J; Fárník, M; Slavíček, P

2013-12-07

We investigate the electron ionization of clusters generated in mixed Ar-water expansions. The electron energy dependent ion yields reveal the neutral cluster composition and structure: water clusters fully covered with the Ar solvation shell are formed under certain expansion conditions. The argon atoms shield the embedded (H2O)n clusters resulting in the ionization threshold above ≈15 eV for all fragments. The argon atoms also mediate more complex reactions in the clusters: e.g., the charge transfer between Ar(+) and water occurs above the threshold; at higher electron energies above ~28 eV, an excitonic transfer process between Ar(+)* and water opens leading to new products Ar(n)H(+) and (H2O)(n)H(+). On the other hand, the excitonic transfer from the neutral Ar* state at lower energies is not observed although this resonant process was demonstrated previously in a photoionization experiment. Doubly charged fragments (H2O)(n)H2(2+) and (H2O)(n)(2+) ions are observed and Intermolecular Coulomb decay (ICD) processes are invoked to explain their thresholds. The Coulomb explosion of the doubly charged cluster formed within the ICD process is prevented by the stabilization effect of the argon solvent.

Detecting negative ions on board small satellites

NASA Astrophysics Data System (ADS)

Lepri, S. T.; Raines, J. M.; Gilbert, J. A.; Cutler, J.; Panning, M.; Zurbuchen, T. H.

2017-04-01

Recent measurements near comets, planets, and their satellites have shown that heavy ions, energetic neutral atoms, molecular ions, and charged dust contain a wealth of information about the origin, evolution, and interaction of celestial bodies with their space environment. Using highly sensitive plasma instruments, positively charged heavy ions have been used to trace exospheric and surface composition of comets, planets, and satellites as well as the composition of interplanetary and interstellar dust. While positive ions dominate throughout the heliosphere, negative ions are also produced from surface interactions. In fact, laboratory experiments have shown that oxygen released from rocky surfaces is mostly negatively charged. Negative ions and negatively charged nanograins have been detected with plasma electron analyzers in several different environments (e.g., by Cassini and Rosetta), though more extensive studies have been challenging without instrumentation dedicated to negative ions. We discuss an adaptation of the Fast Imaging Plasma Spectrometer (FIPS) flown on MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) for the measurement of negatively charged particles. MESSENGER/FIPS successfully measured the plasma environment of Mercury from 2011 until 2015, when the mission ended, and has been used to map multiple ion species (H+ through Na+ and beyond) throughout Mercury's space environment. Modifications to the existing instrument design fits within a 3U CubeSat volume and would provide a low mass, low power instrument, ideal for future CubeSat or distributed sensor missions seeking, for the first time, to characterize the contribution of negative particles in the heliospheric plasmas near the planets, moons, comets, and other sources.

The OI/1S/ state - Its quenching by O2 and formation by the dissociative recombination of vibrationally excited O2/+/ ions

NASA Technical Reports Server (NTRS)

Zipf, E. C.

1979-01-01

The rate coefficient for the quenching of metastable O(1S) atoms by O2 was measured as a function of temperature from 250 to 550 K. The resulting Arrhenius expression correlates well with previous laboratory work. It is suggested that the much larger value of the rate coefficient inferred from an analysis of artificial auroral experiment, Precede, may be explained by overestimation of the contribution of O(1S) production from O2(+) dissociative recombination. The possibility that O(1S) atoms are produced only by the dissociative recombination of vibrationally excited O2(+) ions is examined; such excited ions would not exist in the Precede experiment because of the rapid cooling of the ions by resonant charge transfer processes.

ESI-MS of Cucurbituril Complexes Under Negative Polarity.

PubMed

Rodrigues, Maria A A; Mendes, Débora C; Ramamurthy, Vaidhyanathan; Da Silva, José P

2017-11-01

Electrospray ionization mass spectrometry (ESI-MS) is a powerful tool to study host-guest supramolecular interactions. ESI-MS can be used for detailed gas-phase reactivity studies, to clarify the structure, or simply to verify the formation of complexes. Depending on the structure of the host and of the guest, negative and/or positive ESI are used. Here we report the unexpected formation of host-guest complexes between cucurbit[n]urils (n = 7, 8, CB[n]) and amine, styryl pyridine, and styryl pyridine dimer cations, under negative ESI. Non-complexed CB[n] form double charged halide (Br - , Cl - , F - ) adducts. Under negative ESI, halide ions interact with CB[n] outer surface hydrogen atoms. One to one host-guest complexes (1:1) of CB[n] with positive charged guests were also observed as single and double charged ions under negative ESI. The positive charge of guests is neutralized by ion-pairing with halide anions. Depending on the number of positive charges guests retain in the gas phase, one or two additional halide ions are required for neutralization. Complexes 1:2 of CB[8] with styryl pyridines retain two halide ions in the gas phase, one per guest. Styryl pyridine dimers form 1:1 complexes possessing a single extra halide ion and therefore a single positive charge. Negative ESI is sensitive to small structural differences between complexes, distinguishing between 1:2 complexes of styryl pyridine-CB[8] and corresponding 1:1 complexes with the dimer. Negative ESI gives simpler spectra than positive ESI and allows the determination of guest charge state of CB[n] complexes in the gas phase. Graphical Abstract ᅟ.

Effective Electrostatic Interactions Between Two Overall Neutral Surfaces with Quenched Charge Heterogeneity Over Atomic Length Scale

NASA Astrophysics Data System (ADS)

Zhou, S.

2017-12-01

Using Monte Carlo results as a reference, a classical density functional theory ( CDFT) is shown to reliably predict the forces between two heterogeneously charged surfaces immersed in an electrolyte solution, whereas the Poisson-Boltzmann ( PB) theory is demonstrated to deteriorate obviously for the same system even if the system parameters considered fall within the validity range of the PB theory in the homogeneously charged surfaces. By applying the tested CDFT, we study the effective electrostatic potential of mean force ( EPMF) between two face-face planar and hard surfaces of zero net charge on which positive and negative charges are separated and considered to present as discontinuous spots on the inside edges of the two surfaces. Main conclusions are summarized as follows: (i) strength of the EPMF in the surface charge separation case is very sensitively and positively correlated with the surface charge separation level and valency of the salt ion. Particularly, the charge separation level and the salt ion valency have a synergistic effect, which makes high limit of the EPMF strength in the surface charge separation case significantly go beyond that of the ideal homogeneously charged surface counterpart at average surface charge density similar to the average surface positive or negative charge density in the charge separation case. (ii) The surface charge distribution patterns mainly influence sign of the EPMF: symmetrical and asymmetrical patterns induce repulsive and attractive (at small distances) EPMF, respectively; but with low valency salt ions and low charge separation level the opposite may be the case. With simultaneous presence of both higher valency cation and anion, the EPMF can be repulsive at intermediate distances for asymmetrical patterns. (iii) Salt ion size has a significant impact, which makes the EPMF tend to become more and more repulsive with the ion diameter regardless of the surface charge distribution patterns and the valency of the salt ion; whereas if the 1:1 type electrolyte and the symmetrical patterns are considered, then the opposite may be the case. All of these findings can be explained self-consistently from several perspectives: an excess adsorption of the salt ions (induced by the surface charge separation) serving to raise the osmotic pressure between the plates, configuration fine-tuning in the thinner ion adsorption layer driven by the energy decrease principle, direct Coulombic interactions operating between charged objects on the two face-to-face plates involved, and net charge strength in the ion adsorption layer responsible for the net electrostatic repulsion.

Study of photon emission by electron capture during solar nuclei acceleration, 1: Temperature-dependent cross section for charge changing processes

NASA Technical Reports Server (NTRS)

Perez-Peraza, J.; Alvarez, M.; Laville, A.; Gallegos, A.

1985-01-01

The study of charge changing cross sections of fast ions colliding with matter provides the fundamental basis for the analysis of the charge states produced in such interactions. Given the high degree of complexity of the phenomena, there is no theoretical treatment able to give a comprehensive description. In fact, the involved processes are very dependent on the basic parameters of the projectile, such as velocity charge state, and atomic number, and on the target parameters, the physical state (molecular, atomic or ionized matter) and density. The target velocity, may have also incidence on the process, through the temperature of the traversed medium. In addition, multiple electron transfer in single collisions intrincates more the phenomena. Though, in simplified cases, such as protons moving through atomic hydrogen, considerable agreement has been obtained between theory and experiments However, in general the available theoretical approaches have only limited validity in restricted regions of the basic parameters. Since most measurements of charge changing cross sections are performed in atomic matter at ambient temperature, models are commonly based on the assumption of targets at rest, however at Astrophysical scales, temperature displays a wide range in atomic and ionized matter. Therefore, due to the lack of experimental data , an attempt is made here to quantify temperature dependent cross sections on basis to somewhat arbitrary, but physically reasonable assumptions.

An electron cyclotron resonance ion source based low energy ion beam platform.

PubMed

Sun, L T; Shang, Y; Ma, B H; Zhang, X Z; Feng, Y C; Li, X X; Wang, H; Guo, X H; Song, M T; Zhao, H Y; Zhang, Z M; Zhao, H W; Xie, D Z

2008-02-01

To satisfy the requirements of surface and atomic physics study in the field of low energy multiple charge state ion incident experiments, a low energy (10 eV/q-20 keV/q) ion beam platform is under design at IMP. A simple test bench has been set up to test the ion beam deceleration systems. Considering virtues such as structure simplicity, easy handling, compactness, cost saving, etc., an all-permanent magnet ECRIS LAPECR1 [Lanzhou all-permanent magnet electron cyclotron resonance (ECR) ion source No. 1] working at 14.5 GHz has been adopted to produce intense medium and low charge state ion beams. LAPECR1 source has already been ignited. Some intense low charge state ion beams have been produced on it, but the first test also reveals that many problems are existing on the ion beam transmission line. The ion beam transmission mismatches result in the depressed performance of LAPECR1, which will be discussed in this paper. To obtain ultralow energy ion beam, after being analyzed by a double-focusing analyzer magnet, the selected ion beam will be further decelerated by two afocal deceleration lens systems, which is still under design. This design has taken into consideration both ions slowing down and also ion beam focusing. In this paper, the conceptual design of deceleration system will be discussed.

Y-doped Li 8ZrO 6: A Li-Ion Battery Cathode Material with High Capacity

DOE PAGES

Huang, Shuping; Wilson, Benjamin E.; Wang, Bo; ...

2015-08-11

We study—experimentally and theoretically—the energetics, structural changes, and charge flows during the charging and discharging processes for a new high-capacity cathode material, Li 8ZrO 6 (LZO), which we study both pure and yttrium-doped. We quantum mechanically calculated the stable delithiated configurations, the delithiation energy, the charge flow during delithiation, and the stability of the delithiated materials. We find that Li atoms are easier to extract from tetrahedral sites than octahedral ones. We calculate a large average voltage of 4.04 eV vs Li/Li + for delithiation of the first Li atom in a primitive cell, which is confirmed by galvanostatic charge/dischargemore » cycling data. Energy calculations indicate that topotactic delithiation is kinetically favored over decomposition into Li, ZrO 2, and O 2 during the charging process, although the thermodynamic energy of the topotactic reaction is less favorable. When one or two lithium atoms are extracted from a primitive cell of LZO, its volume and structure change little, whereas extraction of the third lithium greatly distorts the layered structure. The Li 6ZrO 6 and Li 5ZrO 6 delithiation products can be thermodynamically metastable to release of O 2. Experimentally, materials with sufficiently small particle size for efficient delithiation and relithiation were achieved within an yttrium-doped LZO/carbon composite cathode that exhibited an initial discharge capacity of at least 200 mAh/g over the first 10 cycles, with 142 mAh/g maintained after 60 cycles. Computations predict that during the charging process, the oxygen ion near the Li vacancy is oxidized for both pure LZO and yttrium-doped LZO, which leads to a small-polaron hole.« less

Y-doped Li 8ZrO 6: A Li-Ion Battery Cathode Material with High Capacity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Shuping; Wilson, Benjamin E.; Wang, Bo

We study—experimentally and theoretically—the energetics, structural changes, and charge flows during the charging and discharging processes for a new high-capacity cathode material, Li 8ZrO 6 (LZO), which we study both pure and yttrium-doped. We quantum mechanically calculated the stable delithiated configurations, the delithiation energy, the charge flow during delithiation, and the stability of the delithiated materials. We find that Li atoms are easier to extract from tetrahedral sites than octahedral ones. We calculate a large average voltage of 4.04 eV vs Li/Li + for delithiation of the first Li atom in a primitive cell, which is confirmed by galvanostatic charge/dischargemore » cycling data. Energy calculations indicate that topotactic delithiation is kinetically favored over decomposition into Li, ZrO 2, and O 2 during the charging process, although the thermodynamic energy of the topotactic reaction is less favorable. When one or two lithium atoms are extracted from a primitive cell of LZO, its volume and structure change little, whereas extraction of the third lithium greatly distorts the layered structure. The Li 6ZrO 6 and Li 5ZrO 6 delithiation products can be thermodynamically metastable to release of O 2. Experimentally, materials with sufficiently small particle size for efficient delithiation and relithiation were achieved within an yttrium-doped LZO/carbon composite cathode that exhibited an initial discharge capacity of at least 200 mAh/g over the first 10 cycles, with 142 mAh/g maintained after 60 cycles. Computations predict that during the charging process, the oxygen ion near the Li vacancy is oxidized for both pure LZO and yttrium-doped LZO, which leads to a small-polaron hole.« less

Frequency stability degradation of an oscillator slaved to a periodically interrogated atomic resonator.

PubMed

Santarelli, G; Audoin, C; Makdissi, A; Laurent, P; Dick, G J; Clairon, A

1998-01-01

Atomic frequency standards using trapped ions or cold atoms work intrinsically in a pulsed mode. Theoretically and experimentally, this mode of operation has been shown to lead to a degradation of the frequency stability due to the frequency noise of the interrogation oscillator. In this paper a physical analysis of this effect has been made by evaluating the response of a two-level atom to the interrogation oscillator phase noise in Ramsey and multi-Rabi interrogation schemes using a standard quantum mechanical approach. This response is then used to calculate the degradation of the frequency stability of a pulsed atomic frequency standard such as an atomic fountain or an ion trap standard. Comparison is made to an experimental evaluation of this effect in the LPTF Cs fountain frequency standard, showing excellent agreement.

Physics Division annual review, 1 April 1980-31 March 1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1982-06-01

Progress in nuclear physics research is reported in the following areas: medium-energy physics (pion reaction mechanisms, high-resolution studies and nuclear structure, and two-nucleon physics with pions and electrons); heavy-ion research at the tandem and superconducting linear accelerator (resonant structure in heavy-ion reactions, fusion cross sections, high angular momentum states in nuclei, and reaction mechanisms and distributions of reaction strengths); charged-particle research; neutron and photonuclear physics; theoretical physics (heavy-ion direct-reaction theory, nuclear shell theory and nuclear structure, nuclear matter and nuclear forces, intermediate-energy physics, microscopic calculations of high-energy collisions of heavy ions, and light ion direct reactions); the superconducting linac; acceleratormore » operations; and GeV electron linac. Progress in atomic and molecular physics research is reported in the following areas: dissociation and other interactions of energetic molecular ions in solid and gaseous targets, beam-foil research and collision dynamics of heavy ions, photoionization- photoelectron research, high-resolution laser rf spectroscopy with atomic and molecular beams, moessbauer effect research, and theoretical atomic physics. Studies on interactions of energetic particles with solids are also described. Publications are listed. (WHK)« less

Local Electric Field Facilitates High-Performance Li-Ion Batteries.

PubMed

Liu, Youwen; Zhou, Tengfei; Zheng, Yang; He, Zhihai; Xiao, Chong; Pang, Wei Kong; Tong, Wei; Zou, Youming; Pan, Bicai; Guo, Zaiping; Xie, Yi

2017-08-22

By scrutinizing the energy storage process in Li-ion batteries, tuning Li-ion migration behavior by atomic level tailoring will unlock great potential for pursuing higher electrochemical performance. Vacancy, which can effectively modulate the electrical ordering on the nanoscale, even in tiny concentrations, will provide tempting opportunities for manipulating Li-ion migratory behavior. Herein, taking CuGeO 3 as a model, oxygen vacancies obtained by reducing the thickness dimension down to the atomic scale are introduced in this work. As the Li-ion storage progresses, the imbalanced charge distribution emerging around the oxygen vacancies could induce a local built-in electric field, which will accelerate the ions' migration rate by Coulomb forces and thus have benefits for high-rate performance. Furthermore, the thus-obtained CuGeO 3 ultrathin nanosheets (CGOUNs)/graphene van der Waals heterojunctions are used as anodes in Li-ion batteries, which deliver a reversible specific capacity of 1295 mAh g -1 at 100 mA g -1 , with improved rate capability and cycling performance compared to their bulk counterpart. Our findings build a clear connection between the atomic/defect/electronic structure and intrinsic properties for designing high-efficiency electrode materials.

Interplay between O2 and SnO2: oxygen ionosorption and spectroscopic evidence for adsorbed oxygen.

PubMed

Gurlo, Alexander

2006-10-13

Tin dioxide is the most commonly used material in commercial gas sensors based on semiconducting metal oxides. Despite intensive efforts, the mechanism responsible for gas-sensing effects on SnO(2) is not fully understood. The key step is the understanding of the electronic response of SnO(2) in the presence of background oxygen. For a long time, oxygen interaction with SnO(2) has been treated within the framework of the "ionosorption theory". The adsorbed oxygen species have been regarded as free oxygen ions electrostatically stabilized on the surface (with no local chemical bond formation). A contradiction, however, arises when connecting this scenario to spectroscopic findings. Despite trying for a long time, there has not been any convincing spectroscopic evidence for "ionosorbed" oxygen species. Neither superoxide ions O(2)(-), nor charged atomic oxygen O,(-) nor peroxide ions O(2)(2-) have been observed on SnO(2) under the real working conditions of sensors. Moreover, several findings show that the superoxide ion does not undergo transformations into charged atomic oxygen at the surface, and represents a dead-end form of low-temperature oxygen adsorption on reduced metal oxide.

Effect of Mg or Ag addition on the evaporation field of Al.

PubMed

Aruga, Yasuhiro; Nako, Hidenori; Tsuneishi, Hidemasa; Hasegawa, Yuki; Tao, Hiroaki; Ichihara, Chikara; Serizawa, Ai

2013-09-01

It is known that the distribution of the charge-states as well as the evaporation field shift to higher values as the specimen temperature is decreased at a constant rate of evaporation. This study has explored the effect of Mg or Ag addition on the evaporation field of Al in terms of the charge state distribution of the field evaporated Al ions. The fractional abundance of Al(2+) ions with respect to the total Al ions in Al-Mg alloy is lower than that in pure Al, whereas it shows higher level in the Al-Ag alloy at lower temperatures. The temperature dependence of the fractional abundance of Al(2+) ions has been also confirmed, suggesting that Al atoms in the Al-Mg alloy need lower evaporation field, while higher field is necessary to evaporate Al atoms in the Al-Ag alloy, compared with pure Al. This tendency is in agreement with that of the evaporation fields estimated theoretically by means of measurements of the work function and calculations of the binding energy of the pure Al, Al-Mg and Al-Ag alloys. Copyright © 2012 Elsevier B.V. All rights reserved.

Excitation of atoms and ions in plasmas by ultra-short electromagnetic pulses

NASA Astrophysics Data System (ADS)

Astapenko, V. A.; Sakhno, S. V.; Svita, S. Yu; Lisitsa, V. S.

2017-02-01

The problem of atoms and ions diagnostics in rarefied and dense plasmas by ultrashort laser pulses (USP) is under consideration. The application of USP provides: 1) excitation from ground states due to their carrier frequency high enough, 2) penetration into optically dense media due to short pulses duration. The excitation from ground atomic states increases sharply populations of excited atomic states in contrast with standard laser induced fluorescence spectroscopy based on radiative transitions between excited atomic states. New broadening parameter in radiation absorption, namely inverse pulse duration time 1/τ appears in addition to standard line-shape width in the profile G(ω). The Lyman-beta absorption spectra for USP are calculated for Holtsmark static broadening mechanism. Excitation of highly charged H-like ions in hot plasmas is described by both Gaussian shapes for Doppler broadening and pulse spectrum resulting in analytical absorption line-shape. USP penetration into optically thick media and corresponding excitation probability are calculated. It is shown a great effect of USP duration on excitation probabilities in optically thick media. The typical situations for plasma diagnostics by USP are discussed in details.

Recent Development of IMP ECR Ion Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, H.W.; Zhang, Z.M.; Sun, L.T.

2005-03-15

Great efforts have been made to develop highly charged ECR ion sources for application of heavy ion accelerator and atomic physics research at IMP in the past few years. The latest development of ECR ion sources at IMP is briefly reviewed. Intense beams with high and intermediate charge states have been produced from IMP LECR3 by optimization of the ion source conditions including rf frequency extended up to 18GHz. 1.1 emA of Ar8+ and 325 e{mu} A of Ar11+ were produced. Dependence of beam emittance on those key parameters of ECR ion source, beam extraction and space charge compensation weremore » experimentally studied at LECR3. Furthermore, an advanced superconducting ECR ion source named SECRAL is being constructed. SECRAL is designed to operate at rf frequency 18-28GHz with axial mirror magnetic fields 3.6-4.0 Tesla at injection, 2.2 Tesla at extraction and sextupole field 2.0 Tesla at the wall. The superconducting magnet with sextupole and three solenoids was tested in a test-cryostat and 95% of designed fields were reached. Construction status and planed schedule of SECRAL are presented.« less

Neutral recycling effects on ITG turbulence

DOE PAGES

Stotler, D. P.; Lang, J.; Chang, C. S.; ...

2017-07-04

Here, the effects of recycled neutral atoms on tokamak ion temperature gradient (ITG) driven turbulence have been investigated in a steep edge pedestal, magnetic separatrix configuration, with the full-f edge gryokinetic code XGC1. An adiabatic electron model has been used; hence, the impacts of neutral particles and turbulence on the density gradient are not considered, nor are electromagnetic turbulence effects. The neutral atoms enhance the ITG turbulence, first, by increasing the ion temperature gradient in the pedestal via the cooling effects of charge exchange and, second, by a relative reduction in themore » $$E\\times B$$ shearing rate.« less

Neutral recycling effects on ITG turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stotler, D. P.; Lang, J.; Chang, C. S.

Here, the effects of recycled neutral atoms on tokamak ion temperature gradient (ITG) driven turbulence have been investigated in a steep edge pedestal, magnetic separatrix configuration, with the full-f edge gryokinetic code XGC1. An adiabatic electron model has been used; hence, the impacts of neutral particles and turbulence on the density gradient are not considered, nor are electromagnetic turbulence effects. The neutral atoms enhance the ITG turbulence, first, by increasing the ion temperature gradient in the pedestal via the cooling effects of charge exchange and, second, by a relative reduction in themore » $$E\\times B$$ shearing rate.« less

Graphene-Like-Graphite as Fast-Chargeable and High-Capacity Anode Materials for Lithium Ion Batteries.

PubMed

Cheng, Qian; Okamoto, Yasuharu; Tamura, Noriyuki; Tsuji, Masayoshi; Maruyama, Shunya; Matsuo, Yoshiaki

2017-11-01

Here we propose the use of a carbon material called graphene-like-graphite (GLG) as anode material of lithium ion batteries that delivers a high capacity of 608 mAh/g and provides superior rate capability. The morphology and crystal structure of GLG are quite similar to those of graphite, which is currently used as the anode material of lithium ion batteries. Therefore, it is expected to be used in the same manner of conventional graphite materials to fabricate the cells. Based on the data obtained from various spectroscopic techniques, we propose a structural GLG model in which nanopores and pairs of C-O-C units are introduced within the carbon layers stacked with three-dimensional regularity. Three types of highly ionic lithium ions are found in fully charged GLG and stored between its layers. The oxygen atoms introduced within the carbon layers seem to play an important role in accommodating a large amount of lithium ions in GLG. Moreover, the large increase in the interlayer spacing observed for fully charged GLG is ascribed to the migration of oxygen atoms within the carbon layer introduced in the state of C-O-C to the interlayer space maintaining one of the C-O bonds.

Coordinate space translation technique for simulation of electronic process in the ion-atom collision.

PubMed

Wang, Feng; Hong, Xuhai; Wang, Jian; Kim, Kwang S

2011-04-21

Recently we developed a theoretical model of ion-atom collisions, which was made on the basis of a time-dependent density functional theory description of the electron dynamics and a classical treatment of the heavy particle motion. Taking advantage of the real-space grid method, we introduce a "coordinate space translation" technique to allow one to focus on a certain space of interest such as the region around the projectile or the target. Benchmark calculations are given for collisions between proton and oxygen over a wide range of impact energy. To extract the probability of charge transfer, the formulation of Lüdde and Dreizler [J. Phys. B 16, 3973 (1983)] has been generalized to ensemble-averaging application in the particular case of O((3)P). Charge transfer total cross sections are calculated, showing fairly good agreements between experimental data and present theoretical results.

Charge transfer of O3+ ions with atomic hydrogen

NASA Astrophysics Data System (ADS)

Wang, J. G.; Stancil, P. C.; Turner, A. R.; Cooper, D. L.

2003-01-01

Charge transfer processes due to collisions of ground state O3+(2s22p 2P) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with existing experimental and theoretical data shows our results to be in better agreement with the measurements than the previous calculations, although problems with some of the state-selective measurements are noted. Our calculations demonstrate that rotational coupling is not important for the total cross section, but for state-selective cross sections, its relevance increases with energy. For the ratios of triplet to singlet cross sections, significant departures from a statistical value are found, generally in harmony with experiment.

Dielectronic recombination of the 4p and 4d open sub-shell tungsten ions

NASA Astrophysics Data System (ADS)

Li, M. J.; Fu, Y. B.; Zhang, G. D.; Zhang, Y. Z.; Dong, C. Z.; Koike, F.

2014-04-01

Dielectronic recombination rate coefficients are given theoretically for several highly charged tungsten ions. As 4p open sub-shell ions, Ga-, Ge-, As-, Br-, Kr-like ions are considered. Rb-like ion is further considered as a 4d open sub-shell ion. Theoretical calculations are carried out using a relativistic atomic code FAC. The effect of configuration interaction is taking into account. Inner-shell electron excitations play a significant role for the dielectronic recombination process. Simple analytical formulae are given for the total rate coefficients by fitting to the presently obtained numerical results.

Charge states and lattice sites of dilute implanted Sn in ZnO

NASA Astrophysics Data System (ADS)

Mølholt, T. E.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Röder, J.; Adoons, V.; Mokhles Gerami, A.; Masenda, H.; Matveyev, Y. A.; Ncube, M.; Unzueta, I.; Bharuth-Ram, K.; Gislason, H. P.; Krastev, P.; Langouche, G.; Naidoo, D.; Ólafsson, S.; Zenkevich, A.; ISOLDE Collaboration

2017-04-01

The common charge states of Sn are 2+  and 4+. While charge neutrality considerations favour 2+  to be the natural charge state of Sn in ZnO, there are several reports suggesting the 4+  state instead. In order to investigate the charge states, lattice sites, and the effect of the ion implantation process of dilute Sn atoms in ZnO, we have performed 119Sn emission Mössbauer spectroscopy on ZnO single crystal samples following ion implantation of radioactive 119In (T ½  =  2.4 min) at temperatures between 96 K and 762 K. Complementary perturbed angular correlation measurements on 111mCd implanted ZnO were also conducted. Our results show that the 2+  state is the natural charge state for Sn in defect free ZnO and that the 4+  charge state is stabilized by acceptor defects created in the implantation process.

Particle Environment Package (PEP) for the ESA JUICE mission

NASA Astrophysics Data System (ADS)

Barabash, Stas; Brandt, Pontus; Wurz, Peter; PEP Team

2016-10-01

PEP is a suite of six (6) sensors arranged in 4 units to measure charged and neutral particles in the Jupiter magnetospheres and at the moons to answer four overarching science questions:1. How does the corotating magnetosphere of Jupiter interact with the complex and diverse environment of Ganymede?2. How does the rapidly rotating magnetosphere of Jupiter interact with the seemingly inert Callisto?3. What are the governing mechanisms and their global impacts of release of material into the Jovian magnetosphere from seemingly inert Europa and active Io?4. How do internal and solar wind drivers cause such energetic, time variable and multi-scale phenomena in the steadily rotating giant magnetosphere of Jupiter?PEP measures positive and negative ions, electrons, exospheric neutral gas, thermal plasma and energetic neutral atoms present in all domains of the Jupiter system over nine decades of energy from < 0.001 eV to > 1 MeV with full angular coverage.PEP provides instantaneous measurements of 3D flow of the ion plasma and composition to understand the magnetosphere and magnetosphere-moon interactions. It also measures instantaneously 3D electron plasma to investigate auroral processes at the moon and Jupiter. Measurements of the angular distributions of energetic electrons at sub-second resolution probe the acceleration mechanisms and magnetic field topology and boundaries.PEP combines global imaging via remote sensing using energetic neutral atoms (ENA) with in-situ measurements and performs global imaging of Europa/Io tori and magnetosphere combined with energetic ion measurements. Using low energy ENAs originating from the particle - surface interaction PEP investigate space weathering of the icy moons by precipitation particles. PEP will first-ever directly sample of the exospheres of Europa, Ganymede, and Callisto with extremely high mass resolution (M/ΔM > 1100).The PEP sensors are (1) an ion mass analyzer, (2) an electron spectrometer, (3) a low energy ENA imager, (4) a high energy ENA and energetic ions imager, (5) an energetic electron sensor, and (6) a neutral gas and ions mass spectrometer.

Population inversion calculations using near resonant charge exchange as a pumping mechanism

NASA Technical Reports Server (NTRS)

Chubb, D. L.; Rose, J. R.

1972-01-01

Near resonance charge exchange between ions of a large ionization potential gas such as helium or neon and vapors of metals such as zinc, cadmium, selenium, or tellurium has produced laser action in the metal ion gas. The possibility of obtaining population inversions in near resonant charge exchange systems (Xe-Ca, Xe-Mg, Xe-Sr, Xe-Ba, Ar-Mg, N-Ca) was investigated. The analysis is an initial value problem that utilizes rate equations for the densities of relevant levels of the laser gas (Ca, Ba, Mg, or Sr) and an electron energy equation. Electron excitation rates are calculated using the Bohr-Thomson approximation for the cross section. Approximations to experimental values of the electron ionization cross section and the ion-atom charge exchange cross section are used. Preliminary results have been obtained for the Ca-Xe system and show that it is possible to obtain gains greater than 10 to the 14th power/m with inversion times up to 8x10 to the minus 7th power second. A possible charge exchange laser system using a MPD arc plasma accelerator is also described.

Kinetic Properties of Solar Wind Silicon and Iron Ions

NASA Astrophysics Data System (ADS)

Janitzek, N. P.; Berger, L.; Drews, C.; Wimmer-Schweingruber, R. F.

2017-12-01

Heavy ions with atomic numbers Z>2 account for less than one percent of the solar wind ions. However, serving as test particles with differing mass and charge, they provide a unique experimental approach to major questions of solar and fundamental plasma physics such as coronal heating, the origin and acceleration of the solar wind and wave-particle interaction in magnetized plasma. Yet the low relative abundances of the heavy ions pose substantial challenges to the instrumentation measuring these species with reliable statistics and sufficient time resolution. As a consequence the numbers of independent measurements and studies are small. The Charge Time-Of-Flight (CTOF) mass spectrometer as part of the Charge, ELement and Isotope Analysis System (CELIAS) onboard the SOlar and Heliospheric Observatory (SOHO) is a linear time-of-flight mass spectrometer which was operated at Lagrangian point L1 in 1996 for a few months only, before it suffered an instrument failure. Despite its short operation time, the CTOF sensor measured solar wind heavy ions with excellent charge state separation, an unprecedented cadence of 5 minutes and very high counting statistics, exceeding similar state-of-the-art instruments by a factor of ten. In contrast to earlier CTOF studies which were based on reduced onboard post-processed data, in our current studies we use raw Pulse Height Analysis (PHA) data providing a significantly increased mass, mass-per-charge and velocity resolution. Focussing on silicon and iron ion measurements, we present an overview of our findings on (1) short time behavior of heavy ion 1D radial velocity distribution functions, (2) differential streaming between heavy ions and solar wind bulk protons, (3) kinetic temperatures of heavy ions. Finally, we compare the CTOF results with measurements of the Solar Wind Ion Composition Spectrometer (SWICS) instrument onboard the Advanced Composition Explorer (ACE).

Ionic Adsorption and Desorption of CNT Nanoropes

PubMed Central

Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

2016-01-01

A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment. PMID:28335306

A Semiempirical Formula for Single-Electron-Capture Cross Sections of Multiply Charged Ions Colliding with H, H2 and He

NASA Astrophysics Data System (ADS)

Nakai, Yohta; Shirai, Toshizo; Tabata, Tatsuo; Ito, Rinsuke

1989-01-01

A universal analytic formula is given for the total cross sections of single-electron capture by multiply-charged ions colliding with H, H2 or He. Values of constants in the formula have been determined by least-squares fit to experimental data collected from the literature. The formula is applicable to ions of almost all atomic species with charge q greater than 4 (for the H and H2 targets) or 5 (for the He target) in the energy region from about 1 to 107 eV amu-1. The root-mean-square deviation of the data from the formula is 29%. The formula shows that the cross sections are proportional to q1.07 at low energies and to q2.86 at high energies. Other trends of the cross sections that can be derived from the formula are also discussed.

Ionic Adsorption and Desorption of CNT Nanoropes.

PubMed

Shang, Jun-Jun; Yang, Qing-Sheng; Yan, Xiao-Hui; He, Xiao-Qiao; Liew, Kim-Meow

2016-09-28

A nanorope is comprised of several carbon nanotubes (CNTs) with different chiralities. A molecular dynamic model is built to investigate the ionic adsorption and desorption of the CNT nanoropes. The charge distribution on the nanorope is obtained by using a modified gradient method based on classical electrostatic theory. The electrostatic interactions among charged carbon atoms are calculated by using the Coulomb law. It was found here that the charged nanorope can adsorb heavy metal ions, and the adsorption and desorption can be realized by controlling the strength of applied electric field. The distance between the ions and the nanorope as well as the amount of ions have an effect on the adsorption capacity of the nanorope. The desorption process takes less time than that of adsorption. The study indicates that the CNT nanorope can be used as a core element of devices for sewage treatment.

Experimental evidence of beam-foil plasma creation during ion-solid interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Prashant, E-mail: prashant@iuac.res.in; Nandi, Tapan

2016-08-15

Charge state evolution of the energetic projectile ions during the passage through thin carbon foils has been revisited using the X-ray spectroscopy technique. Contributions from the bulk and the solid surface in the charge changing processes have been segregated by measuring the charge state distribution of the projectile ions in the bulk of the target during the ion–solid interaction. Interestingly, the charge state distribution measured in the bulk exhibits Lorentzian profile in contrast to the well-known Gaussian structure observed using the electromagnetic methods and the theoretical predictions. The occurrence of such behavior is a direct consequence of the imbalance betweenmore » charge changing processes, which has been seen in various cases of the laboratory plasma. It suggests that the ion-solid collisions constitute high-density, localized plasma in the bulk of the solid target, called the beam-foil plasma. This condensed beam-foil plasma is similar to the high-density solar and stellar plasma which may have practical implementations in various fields, in particular, plasma physics and nuclear astrophysics. The present work suggests further modification in the theoretical charge state distribution calculations by incorporating the plasma coupling effects during the ion–solid interactions. Moreover, the multi-electron capture from the target exit surface has been confirmed through comparison between experimentally measured and theoretically predicted values of the mean charge state of the projectile ions.« less

Plasma Inter-Particle and Particle-Wall Interactions

NASA Astrophysics Data System (ADS)

Patino, Marlene Idy

An improved understanding of plasma inter-particle and particle-wall interactions is critical to the advancement of plasma devices used for space electric propulsion, fusion, high-power communications, and next-generation energy systems. Two interactions of particular importance are (1) ion-atom collisions in the plasma bulk and (2) secondary electron emission from plasma-facing materials. For ion-atom collisions, interactions between fast ions and slow atoms are commonly dominated by charge-exchange and momentum-exchange collisions that are important to understanding the performance and behavior of many plasma devices. To investigate this behavior, this work developed a simple, well-characterized experiment that accurately measures the effects of high energy xenon ions incident on a background of xenon neutral atoms. By comparing these results to both analytical and computational models of ion-atom interactions, we discovered the importance of (1) accurately treating the differential cross-sections for momentum-exchange and charge-exchange collisions over all neutral background pressures, and (2) commonly overlooked interactions, including ion-induced electron emission and neutral-neutral ionization collisions, at high pressures. Data provide vital information on the angular scattering distributions of charge-exchange and momentum-exchange ions at 1.5 keV relevant for ion thrusters, and serve as canonical data for validation of plasma models. This work also investigates electron-induced secondary electron emission behavior relevant to materials commonly considered for plasma thrusters, fusion systems, and many other plasma devices. For such applications, secondary electron emission can alter the sheath potential, which can significantly affect device performance and life. Secondary electron emission properties were measured for materials that are critical to the efficient operation of many plasma devices, including: graphite (for tokamaks, ion thrusters, and traveling wave tubes), lithium (for tokamak walls), tungsten (the most promising material for future tokamaks such as ITER), and nickel (for plasma-enhanced chemistry). Measurements were made for incident electron energies up to 1.5 keV and angles between 0 and 78°. The most significant results from these measurements are as follows: (1) first-ever measurements of naturally-forming tungsten fuzz show a more than 40% reduction in secondary electron emission and an independence on incidence angle; (2) original measurements of lithium oxide show a 2x and 6x increase in secondary electron emission for 17% and 100% oxidation; and (3) unique measurements of Ni(110) single crystal show extrema in secondary electron emission when incidence angle is varied and an up to 36% increase at 0° over polycrystalline nickel. Each of these results are important discoveries for improving plasma devices. For example, from (1), the growth of tungsten fuzz in tokamaks is desirable for minimizing adverse secondary electron emission effects. From (2), the opposite is true for tokamaks with lithium coatings which are oxidized by typical residual gases. From (3), secondary electron emission from Ni(110) catalysts in plasma-enhanced chemistry may facilitate further reactions.

Turbomolecular Pumps for Holding Gases in Open Containers

NASA Technical Reports Server (NTRS)

Keller, John W.; Lorenz, John E.

2010-01-01

Proposed special-purpose turbomolecular pumps denoted turbotraps would be designed, along with mating open containers, to prevent the escape of relatively slowly (thermal) moving gas molecules from the containers while allowing atoms moving at much greater speeds to pass through. In the original intended applications, the containers would be electron-attachment cells, and the contained gases would be vapors of alkali metal atoms moving at thermal speeds that would be of the order of a fraction of 300 meters per second. These cells would be parts of apparatuses used to measure fluxes of neutral atoms incident at kinetic energies in the approximate range of 10 eV to 10 keV (corresponding to typical speeds of the order of 40,000 m/s and higher). The incident energetic neutral atoms would pass through the cells, wherein charge-exchange reactions with the alkali metal atoms would convert the neutral atoms to negative ions, which, in turn, could then be analyzed by use of conventional charged-particle optics.

Investigation of ion beam space charge compensation with a 4-grid analyzer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ullmann, C., E-mail: c.ullmann@gsi.de; Adonin, A.; Berezov, R.

2016-02-15

Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system ofmore » the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown.« less

Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

NASA Astrophysics Data System (ADS)

Yoshigoe, Akitaka; Shiwaku, Hideaki; Kobayashi, Toru; Shimoyama, Iwao; Matsumura, Daiju; Tsuji, Takuya; Nishihata, Yasuo; Kogure, Toshihiro; Ohkochi, Takuo; Yasui, Akira; Yaita, Tsuyoshi

2018-01-01

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs4,5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L2,3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.

Fragmentation of amino acids induced by collisions with low-energy highly charged ions

NASA Astrophysics Data System (ADS)

Piekarski, D. G.; Maclot, S.; Domaracka, A.; Adoui, L.; Alcamí, M.; Rousseau, P.; Díaz-Tendero, S.; Huber, B. A.; Martín, F.

2014-04-01

Fragmentation of amino acids NH2-(CH2)n-COOH (n=1 glycine; n=2 β-alanine and n=3 γ-aminobutyric acid GABA) following collisions with slow highly charged ions has been studied in the gas phase by a combined experimental and theoretical approach. In the experiments, a multi-coincidence detection method was used to deduce the charge state of the molecules before fragmentation. Quantum chemistry calculations have been carried out in the basis of the density functional theory and ab initio molecular dynamics. The combination of both methodologies is essential to unambiguously unravel the different fragmentation pathways.

Recombination-enhanced surface expansion of clusters in intense soft x-ray laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rupp, Daniela; Flückiger, Leonie; Adolph, Marcus

Here, we studied the nanoplasma formation and explosion dynamics of single large xenon clusters in ultrashort, intense x-ray free-electron laser pulses via ion spectroscopy. The simultaneous measurement of single-shot diffraction images enabled a single-cluster analysis that is free from any averaging over the cluster size and laser intensity distributions. The measured charge state-resolved ion energy spectra show narrow distributions with peak positions that scale linearly with final ion charge state. These two distinct signatures are attributed to highly efficient recombination that eventually leads to the dominant formation of neutral atoms in the cluster. The measured mean ion energies exceed themore » value expected without recombination by more than an order of magnitude, indicating that the energy release resulting from electron-ion recombination constitutes a previously unnoticed nanoplasma heating process. This conclusion is supported by results from semiclassical molecular dynamics simulations.« less

Recombination-enhanced surface expansion of clusters in intense soft x-ray laser pulses

DOE PAGES

Rupp, Daniela; Flückiger, Leonie; Adolph, Marcus; ...

2016-10-07

Here, we studied the nanoplasma formation and explosion dynamics of single large xenon clusters in ultrashort, intense x-ray free-electron laser pulses via ion spectroscopy. The simultaneous measurement of single-shot diffraction images enabled a single-cluster analysis that is free from any averaging over the cluster size and laser intensity distributions. The measured charge state-resolved ion energy spectra show narrow distributions with peak positions that scale linearly with final ion charge state. These two distinct signatures are attributed to highly efficient recombination that eventually leads to the dominant formation of neutral atoms in the cluster. The measured mean ion energies exceed themore » value expected without recombination by more than an order of magnitude, indicating that the energy release resulting from electron-ion recombination constitutes a previously unnoticed nanoplasma heating process. This conclusion is supported by results from semiclassical molecular dynamics simulations.« less

Charge Inversion by Electrostatic Complexation: Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Faraudo, Jordi; Travesset, Alex

2007-03-01

Ions near interfaces play an important role in many biological and physico-chemical processes and exhibit a fascinating diverse range of phenomena. A relevant example is charge inversion, where interfacial charges attract counterions in excess of their own nominal charge, thus leading to an inversion of the sign of the interfacial charge. In this work, we argue that in the case of amphiphilic interfaces, charge inversion can be generated by complexation, that is, electrostatic complexes containing several counterions bound to amphiphilic molecules. The formation of these complexes require the presence at the interface of groups with conformational degrees of freedom with many electronegative atoms. We illustrate this mechanism by analyzing all atomic molecular dynamics simulations of a DMPA (Dimirystoil-Phosphatidic acid) phospholipid monolayer in contact with divalent counterions. The results are found to be in agreement with recent experimental results on Langmuir monolayers. We also discuss the implications for biological systems, as Phosphatidic acid is emerging as a key signaling phospholipid.

Atomic hydrogen and nitrogen distributions from atmosphere explorer measurements

NASA Technical Reports Server (NTRS)

Breig, Edward L.

1992-01-01

We were selective as to our approach to research activities, and devoted primary attention to two investigations concerning the global behavior of atomic hydrogen in the Earth's upper atmosphere. We derive the thermospheric concentration of H by applying the condition of charge-exchange equilibrium between hydrogen and oxygen atoms and ions to in-situ measurements of F-region composition and temperature from the series of Atmosphere Explorer (AE) aeronomy satellites. Progress and accomplishments on these chosen research projects are summarized.

Electron shakeoff following the β+ decay of +19Ne and +35Ar trapped ions

NASA Astrophysics Data System (ADS)

Fabian, X.; Fléchard, X.; Pons, B.; Liénard, E.; Ban, G.; Breitenfeldt, M.; Couratin, C.; Delahaye, P.; Durand, D.; Finlay, P.; Guillon, B.; Lemière, Y.; Mauger, F.; Méry, A.; Naviliat-Cuncic, O.; Porobic, T.; Quéméner, G.; Severijns, N.; Thomas, J.-C.

2018-02-01

The electron shakeoff of 19F and 35Cl atoms resulting from the β+ decay of +19Ne and +35Ar ions has been investigated using a Paul trap coupled to a time of flight recoil-ion spectrometer. The charge-state distributions of the recoiling daughter nuclei were compared to theoretical calculations based on the sudden approximation and accounting for subsequent Auger processes. The excellent agreement obtained for 35Cl is not reproduced in 19F. The shortcoming is attributed to the inaccuracy of the independent particle model employed to calculate the primary shakeoff probabilities in systems with rather low atomic numbers. This calls for more elaborate calculations, including explicitly the electron-electron correlations.

Evidence of charge exchange pumping in calcium-xenon system

NASA Technical Reports Server (NTRS)

Chubb, D. L.

1973-01-01

Charge exchange between xenon ions and calcium atoms may produce an inversion between the 5s or 4d and 4p energy levels of the calcium ions. A low power flowing xenon plasma seeded with calcium was utilized to determine if charge exchange or electron collisions populate the 5s and 4d levels Ca(+). Line intensity ratios proportional to the density ratios n5s/n4p and n4d/n4p were measured. From the dependence of these intensity ratios on power input to the xenon plasma it was concluded that charge exchange pumping of the 5s and 4d levels predominates over electron collisional pumping of these levels. Also, by comparing intensity ratios obtained using argon and krypton in place of xenon with those obtained in xenon the same conclusion was made.

Effect of Valence of Counterions on the Structure of Charged Membranes, a Computer Simulation Study

NASA Astrophysics Data System (ADS)

Qiao, Baofu; Olvera de La Cruz, Monica

2012-02-01

Phospholipids have been investigated for a long period, due to its ability of self-assembling into bilayer structures which resemble biological membranes. But most of the studies have been limited on the neutral phosphatidylcholine based lipids. The understanding of charged membranes (e.g., phosphatidylserine) is very limited due to the repulsion between the charged groups on lipids. In the present work, we investigated the effect of different counter-ions on the structures of charged membranes formed by 1,2-dilauroyl-sn-glycoro-3-phospho-L-serine. Three kinds of counterions were investigated, from monovalent, to divalent, to trivalent ions. Molecular dynamics simulations were performed at all-atom level. We have calculated the area per lipid. And the interaction between counterions and COO^- groups was found to dominate over that between counterions and PO4^- groups.

High Time-Resolved Kinetic Temperatures of Solar Wind Minor Ions Measured with SOHO/CELIAS/CTOF

NASA Astrophysics Data System (ADS)

Janitzek, N. P.; Berger, L.; Drews, C.; Wimmer-Schweingruber, R. F.

2017-12-01

Solar wind heavy ions with an atomic number Z > 2 are referred to as minor ions since they represent a fraction of less than one percent of all solar wind ions. They can be therefore regarded as test particles, only reacting to but not driving the dynamics of the solar wind plasma, which makes them a unique diagnostic tool for plasma wave phenomena both in the solar atmosphere and the extended heliosphere. In the past, several studies have investigated the kinetic temperatures of minor ions, but due to low counting statistics these studies are based on ion velocity distribution functions (VDFs) recorded over time periods of several hours. The Charge Time-Of-Flight (CTOF) mass spectrometer as part of the Charge, ELement and Isotope Analysis System (CELIAS) onboard the SOlar and Heliospheric Observatory (SOHO) provides solar wind heavy ion 1D radial VDFs with excellent charge state separation, an unprecedented cadence of 5 minutes and very high counting statistics, exceeding similar state-of-the-art instruments by a factor of ten. In our study, based on CTOF measurements at Langrangian point L1 between DOY 150 and DOY 220 in 1996, we investigate systematically the influence of the VDF time resolution on the derived kinetic temperatures for solar wind silicon and iron ions. The selected ion set spans a wide range of mass-per-charge from 3 amu/e < m/q < 8 amu/e. Therefore, it is suitable for the search of signatures of gyrofrequency-dependent heating processes resulting from the resonant interaction of heavy ions with ion-cyclotron waves.

Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers.

PubMed

Alejo, A; Kar, S; Ahmed, H; Krygier, A G; Doria, D; Clarke, R; Fernandez, J; Freeman, R R; Fuchs, J; Green, A; Green, J S; Jung, D; Kleinschmidt, A; Lewis, C L S; Morrison, J T; Najmudin, Z; Nakamura, H; Nersisyan, G; Norreys, P; Notley, M; Oliver, M; Roth, M; Ruiz, J A; Vassura, L; Zepf, M; Borghesi, M

2014-09-01

A novel method for characterising the full spectrum of deuteron ions emitted by laser driven multi-species ion sources is discussed. The procedure is based on using differential filtering over the detector of a Thompson parabola ion spectrometer, which enables discrimination of deuterium ions from heavier ion species with the same charge-to-mass ratio (such as C(6+), O(8+), etc.). Commonly used Fuji Image plates were used as detectors in the spectrometer, whose absolute response to deuterium ions over a wide range of energies was calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium ion spectrum diagnosed in a recent experimental campaign is presented, which was produced from a thin deuterated plastic foil target irradiated by a high power laser.

Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers

NASA Astrophysics Data System (ADS)

Alejo, A.; Kar, S.; Ahmed, H.; Krygier, A. G.; Doria, D.; Clarke, R.; Fernandez, J.; Freeman, R. R.; Fuchs, J.; Green, A.; Green, J. S.; Jung, D.; Kleinschmidt, A.; Lewis, C. L. S.; Morrison, J. T.; Najmudin, Z.; Nakamura, H.; Nersisyan, G.; Norreys, P.; Notley, M.; Oliver, M.; Roth, M.; Ruiz, J. A.; Vassura, L.; Zepf, M.; Borghesi, M.

2014-09-01

A novel method for characterising the full spectrum of deuteron ions emitted by laser driven multi-species ion sources is discussed. The procedure is based on using differential filtering over the detector of a Thompson parabola ion spectrometer, which enables discrimination of deuterium ions from heavier ion species with the same charge-to-mass ratio (such as C6 +, O8 +, etc.). Commonly used Fuji Image plates were used as detectors in the spectrometer, whose absolute response to deuterium ions over a wide range of energies was calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium ion spectrum diagnosed in a recent experimental campaign is presented, which was produced from a thin deuterated plastic foil target irradiated by a high power laser.

Lithium-ion battery diagnostic and prognostic techniques

DOEpatents

Singh, Harmohan N.

2009-11-03

Embodiments provide a method and a system for determining cell imbalance condition of a multi-cell battery including a plurality of cell strings. To determine a cell imbalance condition, a charge current is applied to the battery and is monitored during charging. The charging time for each cell string is determined based on the monitor of the charge current. A charge time difference of any two cell strings in the battery is used to determine the cell imbalance condition by comparing with a predetermined acceptable charge time difference for the cell strings.

Dissociative double-photoionization of butadiene in the 25-45 eV energy range using 3-D multi-coincidence ion momentum imaging spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oghbaie, Shabnam; Gisselbrecht, Mathieu; Laksman, Joakim

Dissociative double-photoionization of butadiene in the 25-45 eV energy range has been studied with tunable synchrotron radiation using full three-dimensional ion momentum imaging. Using ab initio calculations, the electronic states of the molecular dication below 33 eV are identified. The results of the measurement and calculation show that double ionization from π orbitals selectively triggers twisting about the terminal or central C–C bonds. We show that this conformational rearrangement depends upon the dication electronic state, which effectively acts as a gateway for the dissociation reaction pathway. For photon energies above 33 eV, three-body dissociation channels where neutral H-atom evaporation precedesmore » C–C charge-separation in the dication species appear in the correlation map. The fragment angular distributions support a model where the dication species is initially aligned with the molecular backbone parallel to the polarization vector of the light, indicating a high probability for double-ionization to the “gateway states” for molecules with this orientation.« less

Charged patchy particle models in explicit salt: Ion distributions, electrostatic potentials, and effective interactions.

PubMed

Yigit, Cemil; Heyda, Jan; Dzubiella, Joachim

2015-08-14

We introduce a set of charged patchy particle models (CPPMs) in order to systematically study the influence of electrostatic charge patchiness and multipolarity on macromolecular interactions by means of implicit-solvent, explicit-ion Langevin dynamics simulations employing the Gromacs software. We consider well-defined zero-, one-, and two-patched spherical globules each of the same net charge and (nanometer) size which are composed of discrete atoms. The studied mono- and multipole moments of the CPPMs are comparable to those of globular proteins with similar size. We first characterize ion distributions and electrostatic potentials around a single CPPM. Although angle-resolved radial distribution functions reveal the expected local accumulation and depletion of counter- and co-ions around the patches, respectively, the orientation-averaged electrostatic potential shows only a small variation among the various CPPMs due to space charge cancellations. Furthermore, we study the orientation-averaged potential of mean force (PMF), the number of accumulated ions on the patches, as well as the CPPM orientations along the center-to-center distance of a pair of CPPMs. We compare the PMFs to the classical Derjaguin-Verwey-Landau-Overbeek theory and previously introduced orientation-averaged Debye-Hückel pair potentials including dipolar interactions. Our simulations confirm the adequacy of the theories in their respective regimes of validity, while low salt concentrations and large multipolar interactions remain a challenge for tractable theoretical descriptions.

Mirror symmetric optics design for charge-stripping section in Rare Isotope Science Project

NASA Astrophysics Data System (ADS)

Kim, Hye-Jin; Kim, Hyung-Jin; Jeon, Dong-O.; Hwang, Ji-Gwang; Kim, Eun-San

2013-12-01

The main aim of the Rare Isotope Science Project is to construct a high power heavy-ion accelerator based on the superconducting linear accelerator (SCL). The heavy ion accelerator is a key research facility that will allow ground-breaking research into numerous facets of basic science, such as nuclear physics, astrophysics, atomic physics, life science, medicine and material science. The machine will provide a beam power of 400 kW with a 238U79+ beam of 8 pμA and 200 MeV/u. One of the critical components in the SCL is the charge stripper between the two segments, SCL1 and SCL2, of the SCL. The charge stripper removes electrons from the ion beams to enhance the acceleration efficiency in the subsequent SCL2. To improve the efficiency of acceleration and power in SCL2, the optimal energy of stripped ions in a solid carbon foil stripper was estimated using the code LISE++. The thickness of the solid carbon foil was 300 μg/m2. The charge stripping efficiency of the solid carbon stripper in the present study was approximately 87%. For charge selection from the ions produced by the solid carbon stripper, a dispersive section is needed down-stream of the foil. The designed optics for the dispersive section is based on the mirror-symmetric optics to minimize the effect of high-order aberrations.

Preliminary Ionization Efficiencies of {sup 11}C and {sup 14}O with the LBNL ECR Ion Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Z.Q.; Cerny, J.; Guo, F.Q.

1998-10-05

High charge states, up to fully stripped {sup 11}C and {sup 14}O ion, beams have been produced with the electron cyclotron resonance ion sources (LBNL, ECR and AECR-U) at Lawrence Berkeley National Laboratory. The radioactive atoms of {sup 11}C and {sup 14}O were collected in batch mode with an LN{sub 2} trap and then bled into the ECR ion sources. Ionization efficiency as high as 11% for {sup 11}C{sup 4+} was achieved.

Polarization and charge transfer in the hydration of chloride ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao Zhen; Rogers, David M.; Beck, Thomas L.

2010-01-07

A theoretical study of the structural and electronic properties of the chloride ion and water molecules in the first hydration shell is presented. The calculations are performed on an ensemble of configurations obtained from molecular dynamics simulations of a single chloride ion in bulk water. The simulations utilize the polarizable AMOEBA force field for trajectory generation and MP2-level calculations are performed to examine the electronic structure properties of the ions and surrounding waters in the external field of more distant waters. The ChelpG method is employed to explore the effective charges and dipoles on the chloride ions and first-shell waters.more » The quantum theory of atoms in molecules (QTAIM) is further utilized to examine charge transfer from the anion to surrounding water molecules. The clusters extracted from the AMOEBA simulations exhibit high probabilities of anisotropic solvation for chloride ions in bulk water. From the QTAIM analysis, 0.2 elementary charges are transferred from the ion to the first-shell water molecules. The default AMOEBA model overestimates the average dipole moment magnitude of the ion compared to the quantum mechanical value. The average magnitude of the dipole moment of the water molecules in the first shell treated at the MP2-level, with the more distant waters handled with an AMOEBA effective charge model, is 2.67 D. This value is close to the AMOEBA result for first-shell waters (2.72 D) and is slightly reduced from the bulk AMOEBA value (2.78 D). The magnitude of the dipole moment of the water molecules in the first solvation shell is most strongly affected by the local water-water interactions and hydrogen bonds with the second solvation shell, rather than by interactions with the ion.« less

Modulating the selectivity of affinity absorbents to multi-phosphopeptides by a competitive substitution strategy.

PubMed

Liu, Zheyi; Wang, Fangjun; Chen, Jin; Zhou, Ye; Zou, Hanfa

2016-08-26

Although many affinity adsorbents have been developed for phosphopeptides enrichment, high-specifically capturing the multi-phosphopeptides is still a big challenge. Here, we investigated the mechanism of phosphate ion coordination and substitution on affinity adsorbents surfaces and modulated the selectivity of affinity adsorbents to multi-phosphopeptides based on the different capability of mono- and multi-phosphopeptides in competitively substituting the pre-coordinated phosphate ions at strong acidic condition. We demonstrated both the species of pre-coordinated phosphate ions and the substituting conditions played crucial roles in modulating the enrichment selectivity to multi-phosphopeptides, and the pre-coordinated affinity materials with relative more surfaces positive charges exhibited better enrichment efficiency due to the cooperative effect of electrostatic interaction and competitive substitution. Finally, an enrichment selectivity of 85% to multi-phosphopeptides was feasibly achieved with 66% improvement in identification numbers for complex protein sample extracted from HepG2 cells. Data are available via ProteomeXchange with identifier PXD004252. Copyright © 2016 Elsevier B.V. All rights reserved.

Studies on heavy charged particle interaction, water equivalence and Monte Carlo simulation in some gel dosimeters, water, human tissues and water phantoms

NASA Astrophysics Data System (ADS)

Kurudirek, Murat

2015-09-01

Some gel dosimeters, water, human tissues and water phantoms were investigated with respect to their radiological properties in the energy region 10 keV-10 MeV. The effective atomic numbers (Zeff) and electron densities (Ne) for some heavy charged particles such as protons, He ions, B ions and C ions have been calculated for the first time for Fricke, MAGIC, MAGAT, PAGAT, PRESAGE, water, adipose tissue, muscle skeletal (ICRP), muscle striated (ICRU), plastic water, WT1 and RW3 using mass stopping powers from SRIM Monte Carlo software. The ranges and straggling were also calculated for the given materials. Two different set of mass stopping powers were used to calculate Zeff for comparison. The water equivalence of the given materials was also determined based on the results obtained. The Monte Carlo simulation of the charged particle transport was also done using SRIM code. The heavy ion distribution along with its parameters were shown for the given materials for different heavy ions. Also the energy loss and damage events in water when irradiated with 100 keV heavy ions were studied in detail.

A multiscale model for charge inversion in electric double layers

NASA Astrophysics Data System (ADS)

Mashayak, S. Y.; Aluru, N. R.

2018-06-01

Charge inversion is a widely observed phenomenon. It is a result of the rich statistical mechanics of the molecular interactions between ions, solvent, and charged surfaces near electric double layers (EDLs). Electrostatic correlations between ions and hydration interactions between ions and water molecules play a dominant role in determining the distribution of ions in EDLs. Due to highly polar nature of water, near a surface, an inhomogeneous and anisotropic arrangement of water molecules gives rise to pronounced variations in the electrostatic and hydration energies of ions. Classical continuum theories fail to accurately describe electrostatic correlations and molecular effects of water in EDLs. In this work, we present an empirical potential based quasi-continuum theory (EQT) to accurately predict the molecular-level properties of aqueous electrolytes. In EQT, we employ rigorous statistical mechanics tools to incorporate interatomic interactions, long-range electrostatics, correlations, and orientation polarization effects at a continuum-level. Explicit consideration of atomic interactions of water molecules is both theoretically and numerically challenging. We develop a systematic coarse-graining approach to coarse-grain interactions of water molecules and electrolyte ions from a high-resolution atomistic scale to the continuum scale. To demonstrate the ability of EQT to incorporate the water orientation polarization, ion hydration, and electrostatic correlations effects, we simulate confined KCl aqueous electrolyte and show that EQT can accurately predict the distribution of ions in a thin EDL and also predict the complex phenomenon of charge inversion.

The accuracy of ab initio calculations without ab initio calculations for charged systems: Kriging predictions of atomistic properties for ions in aqueous solutions

NASA Astrophysics Data System (ADS)

Di Pasquale, Nicodemo; Davie, Stuart J.; Popelier, Paul L. A.

2018-06-01

Using the machine learning method kriging, we predict the energies of atoms in ion-water clusters, consisting of either Cl- or Na+ surrounded by a number of water molecules (i.e., without Na+Cl- interaction). These atomic energies are calculated following the topological energy partitioning method called Interacting Quantum Atoms (IQAs). Kriging predicts atomic properties (in this case IQA energies) by a model that has been trained over a small set of geometries with known property values. The results presented here are part of the development of an advanced type of force field, called FFLUX, which offers quantum mechanical information to molecular dynamics simulations without the limiting computational cost of ab initio calculations. The results reported for the prediction of the IQA components of the energy in the test set exhibit an accuracy of a few kJ/mol, corresponding to an average error of less than 5%, even when a large cluster of water molecules surrounding an ion is considered. Ions represent an important chemical system and this work shows that they can be correctly taken into account in the framework of the FFLUX force field.

Evaluation of the constant potential method in simulating electric double-layer capacitors

NASA Astrophysics Data System (ADS)

Wang, Zhenxing; Yang, Yang; Olmsted, David L.; Asta, Mark; Laird, Brian B.

2014-11-01

A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO4-acetonitrile/graphite EDLC. At low potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of "inner-sphere adsorbed" Li+ ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li+ ions to the electrode surface.

Charge transfer between O6+ and atomic hydrogen

NASA Astrophysics Data System (ADS)

Wu, Y.; Stancil, P. C.; Liebermann, H. P.; Buenker, R. J.; Schultz, D. R.; Hui, Y.

2011-05-01

The charge exchange process has been found to play a dominant role in the production of X-rays and/or EUV photons observed in cometary and planetary atmospheres and from the heliosphere. Charge transfer cross sections, especially state-selective cross sections, are necessary parameters in simulations of X-ray emission. In the present work, charge transfer due to collisions of ground state O6+(1s2 1 S) with atomic hydrogen has been investigated theoretically using the quantum-mechanical molecular-orbital close-coupling method (QMOCC). The multi-reference single- and double-excitation configuration interaction approach (MRDCI) has been applied to compute the adiabatic potential and nonadiabatic couplings, and the atomic basis sets used have been optimized with the method proposed previously to obtain precise potential data. Total and state-selective cross sections are calculated for energies between 10 meV/u and 10 keV/u. The QMOCC results are compared to available experimental and theoretical data as well as to new atomic-orbital close-coupling (AOCC) and classical trajectory Monte Carlo (CTMC) calculations. A recommended set of cross sections, based on the MOCC, AOCC, and CTMC calculations, is deduced which should aid in X-ray modeling studies.

Solar wind charge exchange in laboratory - Observation of forbidden X-ray transitions

NASA Astrophysics Data System (ADS)

Numadate, Naoki; Shimaya, Hirofumi; Ishida, Takuya; Okada, Kunihiro; Nakamura, Nobuyuki; Tanuma, Hajime

2017-10-01

We have reproduced solar wind charge exchange collisions of hydrogen-like O7+ ions with He gas at collision energies of 42 keV in the laboratory and observed the forbidden transition of 1s21S0 -1s2s 3S1 in helium-like O6+ ions produced by single electron capture. The measured soft X-ray spectrum had a peak at 560 eV which corresponds to the energy of the forbidden 1s21S0 -1s2s 3S1 transition in the O6+ ion, and a reasonable energy difference between peak positions of the forbidden and resonance lines was found, which ensured that we succeeded in observing the forbidden transition of O6+ ions. The dominant electron capture level in the collision of O7+ ions with He can be estimated to be a principal quantum number n = 4 by the classical over barrier model and the two-center atomic orbital close coupling method. After the charge exchange, the population of the 1s2s state becomes large due to cascade transitions from the higher excited states, so the long-lived forbidden transition to the 1s21S0 ground state is one of main features observed in the charge exchange spectra.

Multi-functional spintronic devices based on boron- or aluminum-doped silicene nanoribbons

NASA Astrophysics Data System (ADS)

Liu, Y. S.; Dong, Y. J.; Zhang, J.; Yu, H. L.; Feng, J. F.; Yang, X. F.

2018-03-01

Zigzag silicene nanoribbons (ZSiNRs) in the ferromagnetic edge ordering have a metallic behavior, which limits their applications in spintronics. Here a robustly half-metallic property is achieved by the boron substitution doping at the edge of ZSiNRs. When the impurity atom is replaced by the aluminum atom, the doped ZSiNRs possess a spin semiconducting property. Its band gap is suppressed with the increase of ribbon’s width, and a pure thermal spin current is achieved by modulating ribbon’s width. Moreover, a negative differential thermoelectric resistance in the thermal charge current appears as the temperature gradient increases, which originates from the fact that the spin-up and spin-down thermal charge currents have diverse increasing rates at different temperature gradient regions. Our results put forward a promising route to design multi-functional spintronic devices which may be applied in future low-power-consumption technologies.

Optimizing charge breeding techniques for ISOL facilities in Europe: Conclusions from the EMILIE project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delahaye, P., E-mail: delahaye@ganil.fr; Jardin, P.; Maunoury, L.

The present paper summarizes the results obtained from the past few years in the framework of the Enhanced Multi-Ionization of short-Lived Isotopes for Eurisol (EMILIE) project. The EMILIE project aims at improving the charge breeding techniques with both Electron Cyclotron Resonance Ion Sources (ECRIS) and Electron Beam Ion Sources (EBISs) for European Radioactive Ion Beam (RIB) facilities. Within EMILIE, an original technique for debunching the beam from EBIS charge breeders is being developed, for making an optimal use of the capabilities of CW post-accelerators of the future facilities. Such a debunching technique should eventually resolve duty cycle and time structuremore » issues which presently complicate the data-acquisition of experiments. The results of the first tests of this technique are reported here. In comparison with charge breeding with an EBIS, the ECRIS technique had lower performance in efficiency and attainable charge state for metallic ion beams and also suffered from issues related to beam contamination. In recent years, improvements have been made which significantly reduce the differences between the two techniques, making ECRIS charge breeding more attractive especially for CW machines producing intense beams. Upgraded versions of the Phoenix charge breeder, originally developed by LPSC, will be used at SPES and GANIL/SPIRAL. These two charge breeders have benefited from studies undertaken within EMILIE, which are also briefly summarized here.« less

Multi-dimensional effects in radiation pressure acceleration of ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tripathi, V. K., E-mail: tripathivipin@yahoo.co.in

A laser carries momentum. On reflection from an ultra-thin overdense plasma foil, it deposits recoil momentum on the foil, i.e. exerts radiation pressure on the foil electrons and pushes them to the rear. The space charge field thus created takes the ions along, accelerating the electron-ion double layer as a single unit. When the foil has surface ripple, of wavelength comparable to laser wavelength, the radiation pressure acts non-uniformly on the foil and the perturbation grows as Reyleigh-Taylor (RT) instability as the foil moves. The finite spot size of the laser causes foil to bend. These effects limit the quasi-monomore » energy acceleration of ions. Multi-ion foils, e.g., diamond like carbon foil embedded with protons offer the possibility of suppressing RT instability.« less

Computer Model Of Fragmentation Of Atomic Nuclei

NASA Technical Reports Server (NTRS)

Wilson, John W.; Townsend, Lawrence W.; Tripathi, Ram K.; Norbury, John W.; KHAN FERDOUS; Badavi, Francis F.

1995-01-01

High Charge and Energy Semiempirical Nuclear Fragmentation Model (HZEFRG1) computer program developed to be computationally efficient, user-friendly, physics-based program for generating data bases on fragmentation of atomic nuclei. Data bases generated used in calculations pertaining to such radiation-transport applications as shielding against radiation in outer space, radiation dosimetry in outer space, cancer therapy in laboratories with beams of heavy ions, and simulation studies for designing detectors for experiments in nuclear physics. Provides cross sections for production of individual elements and isotopes in breakups of high-energy heavy ions by combined nuclear and Coulomb fields of interacting nuclei. Written in ANSI FORTRAN 77.

Efficient Means of Detecting Neutral Atoms in Space

NASA Astrophysics Data System (ADS)

Zinicola, W. N.

2006-12-01

This summer, The Society of Physics Students granted me the opportunity to participate in an internship for The National Aeronautics and Space Administration (NASA) and The University of Maryland. Our chief interest was analyzing low energy neutral atoms that were created from random interactions of ions in space plasma. From detecting these neutrals one can project a image of what the plasma's composition is, and how this plasma changes through interactions with the solar wind. Presently, low energy neutral atom detectors have poor efficiency, typically in the range of 1%. Our goal was to increase this efficiency. To detect low energy neutrals we must first convert them from neutral molecules to negatively charged ions. Once converted, these "new" negatively charged ions can be easily detected and completely analyzed giving us information about their energy, mass, and instantaneous direction. The efficiency of the detector is drastically affected by the surface used for converting these neutrals. My job was first to create thin metal conversion surfaces. Then, using an X-ray photoelectron spectrometer, analyze atomic surface composition and gather work function values. Once the work function values were known we placed the surfaces in our neutral detector and measured their conversion efficiencies. Finally, a relation between the work function of the metal surface an its conversion efficiency was generated. With this relationship accurately measured one could use this information to help give suggestions on what surface would be the best to increase our detection efficiency. If we could increase the efficiency of these low energy neutral atom detectors by even 1% we would be able to decrease the size of the detector therefore making it cheaper and more applicable for space exploration.* * A special thanks to Dr. Michael Coplan of the University of Maryland for his support and guidance through all my research.

Cation Recombination Energy/Coulomb Repulsion Effects in ETD/ECD as Revealed by Variation of Charge per Residue at Fixed Total Charge

PubMed Central

Mentinova, Marija; Crizer, David M.; Baba, Takashi; McGee, William M.; Glish, Gary L.; McLuckey, Scott A.

2013-01-01

Electron capture dissociation (ECD) and electron transfer dissociation (ETD) experiments in electrodynamic ion traps operated in the presence of a bath gas in the 1–10 mTorr range have been conducted on a common set of doubly protonated model peptides of the form X(AG)nX (X = lysine, arginine, or histidine, n=1, 2, or 4). The partitioning of reaction products was measured using thermal electrons, anions of azobenzene, and anions of 1,3-dinitrobenzene as reagents. Variation of n alters the charge per residue of the peptide cation, which affects recombination energy. The ECD experiments showed that H-atom loss is greatest for the n=1 peptides and decreases as n increases. Proton transfer in ETD, on the other hand, is expected to increase as charge per residue decreases (i.e., as n increases). These opposing tendencies were apparent in the data for the K(AG)nK peptides. H-atom loss appeared to be more prevalent in ECD than in ETD and is rationalized on the basis of either internal energy differences, differences in angular momentum transfer associated with the electron capture versus electron transfer processes, or a combination of the two. The histidine peptides showed the greatest extent of charge reduction without dissociation, the arginine peptides showed the greatest extent of side-chain cleavages, and the lysine peptides generally showed the greatest extent of partitioning into the c/z•-product ion channels. The fragmentation patterns for the complementary c- and z•-ions for ETD and ECD were found to be remarkably similar, particularly for the peptides with X = lysine. PMID:23568028

Hydrated proton and hydroxide charge transfer at the liquid/vapor interface of water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soniat, Marielle; Rick, Steven W., E-mail: srick@uno.edu; Kumar, Revati

2015-07-28

The role of the solvated excess proton and hydroxide ions in interfacial properties is an interesting scientific question with applications in a variety of aqueous behaviors. The role that charge transfer (CT) plays in interfacial behavior is also an unsettled question. Quantum calculations are carried out on clusters of water with an excess proton or a missing proton (hydroxide) to determine their CT. The quantum results are applied to analysis of multi-state empirical valence bond trajectories. The polyatomic nature of the solvated excess proton and hydroxide ion results in directionally dependent CT, depending on whether a water molecule is amore » hydrogen bond donor or acceptor in relation to the ion. With polyatomic molecules, CT also depends on the intramolecular bond distances in addition to intermolecular distances. The hydrated proton and hydroxide affect water’s liquid/vapor interface in a manner similar to monatomic ions, in that they induce a hydrogen-bonding imbalance at the surface, which results in charged surface waters. This hydrogen bond imbalance, and thus the charged waters at the surface, persists until the ion is at least 10 Å away from the interface.« less

Liouville master equation for multi-electron dynamics during ion-surface interactions

NASA Astrophysics Data System (ADS)

Wirtz, L.; Reinhold, C. O.; Lemell, C.; Burgdorfer, J.

2003-05-01

We present a simulation of the neutralization of highly charged ions in front of a LiF(100) surface including the close-collision regime above the surface. Our approach employs a Monte-Carlo solution of the Liouville master equation for the joint probability density of the ionic motion and the electronic population of the projectile and the target surface. It includes single as well as double particle-hole (de)excitation processes and incorporates electron correlation effects through the conditional dynamics of population strings. The input in terms of elementary one- and two-electron transfer rates is determined from CTMC calculations as well as quantum mechanical Auger calculations. For slow projectiles and normal incidence, the ionic motion depends sensitively on the interplay between image acceleration towards the surface and repulsion by an ensemble of positive hole charges in the surface (``trampoline effect"). For Ne10+ ions we find that image acceleration dominates and no collective backscattering high above the surface takes place. For grazing incidence, our simulation delineates the pathways to complete neutralization. In accordance with recent experimental observations, most ions are reflected as neutrals or even as singly charged negative particles, irrespective of the charge state of the incoming ion.

K-P-Burgers equation in negative ion-rich relativistic dusty plasma including the effect of kinematic viscosity

NASA Astrophysics Data System (ADS)

Dev, A. N.; Deka, M. K.; Sarma, J.; Saikia, D.; Adhikary, N. C.

2016-10-01

The stationary solution is obtained for the K-P-Burgers equation that describes the nonlinear propagations of dust ion acoustic waves in a multi-component, collisionless, un-magnetized relativistic dusty plasma consisting of electrons, positive and negative ions in the presence of charged massive dust grains. Here, the Kadomtsev-Petviashvili (K-P) equation, three-dimensional (3D) Burgers equation, and K-P-Burgers equations are derived by using the reductive perturbation method including the effects of viscosity of plasma fluid, thermal energy, ion density, and ion temperature on the structure of a dust ion acoustic shock wave (DIASW). The K-P equation predictes the existences of stationary small amplitude solitary wave, whereas the K-P-Burgers equation in the weakly relativistic regime describes the evolution of shock-like structures in such a multi-ion dusty plasma.

Evaluation of methods for trace-element determination with emphasis on their usability in the clinical routine laboratory.

PubMed

Bolann, B J; Rahil-Khazen, R; Henriksen, H; Isrenn, R; Ulvik, R J

2007-01-01

Commonly used techniques for trace-element analysis in human biological material are flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Elements that form volatile hydrides, first of all mercury, are analysed by hydride generation techniques. In the absorption techniques the samples are vaporized into free, neutral atoms and illuminated by a light source that emits the atomic spectrum of the element under analysis. The absorbance gives a quantitative measure of the concentration of the element. ICP-AES and ICP-MS are multi-element techniques. In ICP-AES the atoms of the sample are excited by, for example, argon plasma at very high temperatures. The emitted light is directed to a detector, and the optical signals are processed to values for the concentrations of the elements. In ICP-MS a mass spectrometer separates and detects ions produced by the ICP, according to their mass-to-charge ratio. Dilution of biological fluids is commonly needed to reduce the effect of the matrix. Digestion using acids and microwave energy in closed vessels at elevated pressure is often used. Matrix and spectral interferences may cause problems. Precautions should be taken against trace-element contamination during collection, storage and processing of samples. For clinical problems requiring the analysis of only one or a few elements, the use of FAAS may be sufficient, unless the higher sensitivity of GFAAS is required. For screening of multiple elements, however, the ICP techniques are preferable.

High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma.

PubMed

Vodopyanov, A V; Golubev, S V; Khizhnyak, V I; Mansfeld, D A; Nikolaev, A G; Oks, E M; Savkin, K P; Vizir, A V; Yushkov, G Yu

2008-02-01

A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 micros, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed.

Theory of the polarization of highly charged ions in storage rings: Production, preservation, observation and application to the search for a violation of the fundamental symmetries

NASA Astrophysics Data System (ADS)

Bondarevskaya, A.; Prozorov, A.; Labzowsky, L.; Plunien, G.; Liesen, D.; Bosch, F.

2011-10-01

Theoretical concepts for the production, preservation and control of polarized highly charged ion beams in storage rings are investigated. It is argued that hydrogen-like ions can be polarized efficiently by optical pumping of the Zeeman sublevels of ground state hyperfine levels and that the maximum achievable nuclear polarization exceeds 90%. In order to study the preservation of the polarization during the ion motion through the magnetic system of the ring, the concept of the instantaneous quantization axis is introduced. It is suggested that the employment of “Siberian snakes” may help to preserve the ion beam polarization in the ring. The control of the beam polarization can be achieved by different methods: by measuring the Stokes parameters for the emitted photons or by observing the angular dependence of the transition rates for polarized ions. The important motivation for the production of polarized ion beams is the possibility to observe parity nonconservation effects in the hyperfine-quenched transitions in helium-like highly charged ions, where these effects can reach an unprecedented high value for atomic physics. The possible observation of parity nonconservation effects connected with the nuclear anapole moment is also discussed. A method for the observation of the electric dipole moment of an electron in a storage ring with a polarized highly charged ion beam is proposed. This method allows, in principle, to improve the existing boundaries for the electric dipole moment of an electron. However, the requirements of the corresponding experiment are very stringent.

Atomic Data for Neutron-capture Elements I. Photoionization and Recombination Properties of Low-charge Selenium Ions

NASA Technical Reports Server (NTRS)

Sterling, N. C.; Witthoeft, Michael

2011-01-01

We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections. and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis. but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi re1ativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed (Delta)n = 0 core excitations, which are important at photoionized plasma temperatures. We find that DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (approx.10(exp 4) K). In order to estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and also tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and approx.10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. These data are available at the CDS, and fitting coefficients to the total RR and DR rate coefficients are presented. The results are suitable for incorporation into photoionization codes used to numerically simulate astrophysical nebulae, and will enable robust determinations of nebular Se abundances.

Superatom spectroscopy and the electronic state correlation between elements and isoelectronic molecular counterparts.

PubMed

Peppernick, Samuel J; Gunaratne, K D Dasitha; Castleman, A W

2010-01-19

Detailed in the present investigation are results pertaining to the photoelectron spectroscopy of negatively charged atomic ions and their isoelectronic molecular counterparts. Experiments utilizing the photoelectron imaging technique are performed on the negative ions of the group 10 noble metal block (i.e. Ni-, Pd-, and Pt-) of the periodic table at a photon energy of 2.33 eV (532 nm). The accessible electronic transitions, term energies, and orbital angular momentum components of the bound electronic states in the atom are then compared with photoelectron images collected for isoelectronic early transition metal heterogeneous diatomic molecules, M-X- (M = Ti,Zr,W; X = O or C). A superposition principle connecting the spectroscopy between the atomic and molecular species is observed, wherein the electronic structure of the diatomic is observed to mimic that present in the isoelectronic atom. The molecular ions studied in this work, TiO-, ZrO-, and WC- can then be interpreted as possessing superatomic electronic structures reminiscent of the isoelectronic elements appearing on the periodic table, thereby quantifying the superatom concept.

Graphene Visualizes the Ion Distribution on Air-Cleaved Mica.

PubMed

Bampoulis, Pantelis; Sotthewes, Kai; Siekman, Martin H; Zandvliet, Harold J W; Poelsema, Bene

2017-03-06

The distribution of potassium (K + ) ions on air-cleaved mica is important in many interfacial phenomena such as crystal growth, self-assembly and charge transfer on mica. However, due to experimental limitations to nondestructively probe single ions and ionic domains, their exact lateral organization is yet unknown. We show, by the use of graphene as an ultra-thin protective coating and scanning probe microscopies, that single potassium ions form ordered structures that are covered by an ice layer. The K + ions prefer to minimize the number of nearest neighbour K + ions by forming row-like structures as well as small domains. This trend is a result of repulsive ionic forces between adjacent ions, weakened due to screening by the surrounding water molecules. Using high resolution conductive atomic force microscopy maps, the local conductance of the graphene is measured, revealing a direct correlation between the K + distribution and the structure of the ice layer. Our results shed light on the local distribution of ions on the air-cleaved mica, solving a long-standing enigma. They also provide a detailed understanding of charge transfer from the ionic domains towards graphene.

Experimental observation of charge-shift bond in fluorite CaF2.

PubMed

Stachowicz, Marcin; Malinska, Maura; Parafiniuk, Jan; Woźniak, Krzysztof

2017-08-01

On the basis of a multipole refinement of single-crystal X-ray diffraction data collected using an Ag source at 90 K to a resolution of 1.63 Å -1 , a quantitative experimental charge density distribution has been obtained for fluorite (CaF 2 ). The atoms-in-molecules integrated experimental charges for Ca 2+ and F - ions are +1.40 e and -0.70 e, respectively. The derived electron-density distribution, maximum electron-density paths, interaction lines and bond critical points along Ca 2+ ...F - and F - ...F - contacts revealed the character of these interactions. The Ca 2+ ...F - interaction is clearly a closed shell and ionic in character. However, the F - ...F - interaction has properties associated with the recently recognized type of interaction referred to as `charge-shift' bonding. This conclusion is supported by the topology of the electron localization function and analysis of the quantum theory of atoms in molecules and crystals topological parameters. The Ca 2+ ...F - bonded radii - measured as distances from the centre of the ion to the critical point - are 1.21 Å for the Ca 2+ cation and 1.15 Å for the F - anion. These values are in a good agreement with the corresponding Shannon ionic radii. The F - ...F - bond path and bond critical point is also found in the CaF 2 crystal structure. According to the quantum theory of atoms in molecules and crystals, this interaction is attractive in character. This is additionally supported by the topology of non-covalent interactions based on the reduced density gradient.

The Structure of the Heliosphere as Seen from In Situ and Remote Observations

NASA Astrophysics Data System (ADS)

Pogorelov, N. V.; Heerikhuisen, J.; Kim, T. K.; Zhang, M.

2017-12-01

The heliosphere is formed due to interaction between the solar wind (SW) and local interstellar medium (LISM). The shape and position of the heliospheric boundary, the heliopause, in space depend on the parameters of interacting plasma flows. The interplay between the asymmetrizing effect of the interstellar magnetic field and charge exchange between ions and neutral atoms plays an important role in the SW-LISM interaction. By performing three-dimensional, MHD plasma / kinetic neutral atom simulations, we describe the structure of the outer heliosheath (OHS) - the LISM plasma region affected by the presence of the heliosphere - and analyze quantitatively the distributions in front of the heliopause. It is shown that charge exchange modifies the LISM plasma to such extent that the contribution of a shock transition to the total variation of plasma parameters becomes small even if the LISM velocity exceeds the fast magnetosonic speed in the unperturbed medium. By performing adaptive mesh refinement simulations, we show that a distinct boundary layer of decreased plasma density and enhanced magnetic field should be observed on the interstellar side of the heliopause. We show that this behavior is in agreement with the plasma oscillations of increasing frequency observed by the plasma wave instrument onboard Voyager 1. Numerical results are presented that reproduce shocks that pass by Voyager 1 in the OHS. We demonstrate that Voyager observations in the inner heliosheath between the heliospheric termination shock and the heliopause are consistent with dissipation of the heliospheric magnetic field. The effect of pickup ions is discussed in the context of in situ measurements. We also show that multi-TeV cosmic ray anisotropy can serve as an imager of the heliosphere due to its effect on the LISM properties. In particular, both the bow wave and the heliotail reveal themselves as characteristic features in the TeV flux images. The choice of LISM parameters in this analysis is based on the simulations that fit observations of energetic neutral atoms performed by IBEX. In particular, the position of the IBEX ribbon on the celestial sphere is strongly dependent on the choice of the plane that contains the vectors of velocity and magnetic field in the unperturbed LISM.

Ionic strength independence of charge distributions in solvation of biomolecules

NASA Astrophysics Data System (ADS)

Virtanen, J. J.; Sosnick, T. R.; Freed, K. F.

2014-12-01

Electrostatic forces enormously impact the structure, interactions, and function of biomolecules. We perform all-atom molecular dynamics simulations for 5 proteins and 5 RNAs to determine the dependence on ionic strength of the ion and water charge distributions surrounding the biomolecules, as well as the contributions of ions to the electrostatic free energy of interaction between the biomolecule and the surrounding salt solution (for a total of 40 different biomolecule/solvent combinations). Although water provides the dominant contribution to the charge density distribution and to the electrostatic potential even in 1M NaCl solutions, the contributions of water molecules and of ions to the total electrostatic interaction free energy with the solvated biomolecule are comparable. The electrostatic biomolecule/solvent interaction energies and the total charge distribution exhibit a remarkable insensitivity to salt concentrations over a huge range of salt concentrations (20 mM to 1M NaCl). The electrostatic potentials near the biomolecule's surface obtained from the MD simulations differ markedly, as expected, from the potentials predicted by continuum dielectric models, even though the total electrostatic interaction free energies are within 11% of each other.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badnell, N. R.; Ballance, C. P.

Modeling the spectral emission of low-charge iron group ions enables the diagnostic determination of the local physical conditions of many cool plasma environments such as those found in H II regions, planetary nebulae, active galactic nuclei, etc. Electron-impact excitation drives the population of the emitting levels and, hence, their emissivities. By carrying-out Breit-Pauli and intermediate coupling frame transformation (ICFT) R-matrix calculations for the electron-impact excitation of Fe{sup 2+}, which both use the exact same atomic structure and the same close-coupling expansion, we demonstrate the validity of the application of the powerful ICFT method to low-charge iron group ions. This ismore » in contradiction to the finding of Bautista et al., who carried-out ICFT and Dirac R-matrix calculations for the same ion. We discuss possible reasons.« less

Deciphering the "chemical" nature of the exotic isotopes of hydrogen by the MC-QTAIM analysis: the positively charged muon and the muonic helium as new members of the periodic table.

PubMed

Goli, Mohammad; Shahbazian, Shant

2014-04-14

This report is a primarily survey on the chemical nature of some exotic species containing the positively charged muon and the muonic helium, i.e., the negatively charged muon plus helium nucleus, as exotic isotopes of hydrogen, using the newly developed multi-component quantum theory of atoms in molecules (MC-QTAIM) analysis, employing ab initio non-Born-Oppenhiemer wavefunctions. Accordingly, the "atoms in molecules" analysis performed on various asymmetric exotic isotopomers of the hydrogen molecule, recently detected experimentally [Science, 2011, 331, 448], demonstrates that both the exotic isotopes are capable of forming atoms in molecules and retaining the identity of hydrogen atoms. Various derived properties of atomic basins containing the muonic helium cast no doubt that apart from its short life time, it is a heavier isotope of hydrogen while the properties of basins containing the positively charged muon are more remote from those of the orthodox hydrogen basins, capable of appreciable donation of electrons as well as large charge polarization. However, with some tolerance, they may also be categorized as hydrogen basins though with a smaller electronegativity. All in all, the present study also clearly demonstrates that the MC-QTAIM analysis is an efficient approach to decipher the chemical nature of species containing exotic constituents, which are difficult to elucidate by experimental and/or alternative theoretical schemes.

Excitation and charge transfer in low-energy hydrogen atom collisions with neutral iron

NASA Astrophysics Data System (ADS)

Barklem, P. S.

2018-05-01

Data for inelastic processes due to hydrogen atom collisions with iron are needed for accurate modelling of the iron spectrum in late-type stars. Excitation and charge transfer in low-energy Fe+H collisions is studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multi-channel Landau-Zener model. An extensive calculation including 166 covalent states and 25 ionic states is presented and rate coefficients are calculated for temperatures in the range 1000-20 000 K. The largest rates are found for charge transfer processes to and from two clusters of states around 6.3 and 6.6 eV excitation, corresponding in both cases to active 4d and 5p electrons undergoing transfer. Excitation and de-excitation processes among these two sets of states are also significant. Full Tables and rate coefficient data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A90

Electron Emission in Highly Charged Ion-Atom Collisions

NASA Astrophysics Data System (ADS)

Liao, Chunlei

1995-01-01

This dissertation addresses the problem of electron emission in highly charged ion-atom collisions. The study is carried out by measuring doubly differential cross sections (DDCS) of emitted electrons for projectiles ranging from fluorine up to gold at ejection angles (theta _{L}) from 0^circ to 70^circ with respect to the beam direction. Prominent features are a very strong forward peaked angular distribution of emitted electrons and the appearance of strong diffraction structures in the binary encounter electron (BEe) region for projectiles heavier than chlorine. This is in clear contradiction to the results found with fluorine projectiles, where the BEe production increases slightly with increasing theta_{L} and no structure is observed in the BEe region. Both can be understood in the impulse approximation as elastic scattering of quasi free target electrons in the projectile potential. Our measurements also show that the violation of q ^2 scaling of the DDCS previously established for 0^circ electron spectra persists for all emission angles and almost all electron energies. In ion-atom collisions, besides electrons from target, electrons from projectile ionization are also presented in the emitted electron spectra. Using electron-projectile coincidence technique, different collision channels can be separated. In order to eliminate the speculations of contributions from projectile related capture and loss channels, coincidence studies of diffraction structures are initiated. In the 0^circ electron spectrum of 0.3 MeV/u I^{6+} impacting on H_2, strong autoionization peaks are observed on the shoulders of the cusp peak. The energies of these autoionization lines in the projectile rest frame are determined by high-resolution electron spectroscopy, and collision mechanism is probed by electron-charge state selected projectile coincidence technique.

Effects of Io's volcanos on the plasma torus and Jupiter's magnetosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, A.F.

1980-12-01

Io's volcanism can have dominant effects on Jupiter's magnetosphere. A model is developed in which a neutral gas torus is formed at Io's orbit by volcanic SO/sub 2/ escaping from Io. Ionization and dissociation of volcanic SO/sub 2/ is shown to be the dominant source of plasma in Jupiter's magnetosphere. The failure of Voyager observations to confirm predictions of the magnetic anomaly model is naturally explained. A 30--50 KeV sulfur and oxygen ion plasma is formed in the outer magnetosphere, with density roughly equal to the proton density there, by ionization of sulfur and oxygen atoms on highly eccentric ellipticalmore » orbits around Jupiter. When these atoms are ionized in the outer magnetosphere, they are swept up by the Jovian magnetic field and achieve 30--50 keV energies. Such atoms are created by dissociative attachment of SO/sub 2/ by < or approx. =10 eV electrons. Substantial losses of radiation-belt charged particles result from passage through the neutral gas torus. Such losses can account for observed anomalies in charged particle depletions near Io; these could not be understood in terms of satellite sweeping alone. Substantial ionization energy loss occurs for < or approx. =1 MeV protons and < or approx. =100 keV electrons; losses of < or approx. =1 MeV protons are much greater than for comparable energy electrons. Losses of < or approx. =1 MeV per nucleon ions are also severe. Other consequences of the model include intrinsic time variability in the Jovian magnetosphere, on times > or approx. =10/sup 6/ s, caused by variations in Io's volcanic activity. Charged particle losses in the neutral gas torus tend to yield dumbbell-shaped pitch-angle distributions. Negative ions are predicted in the Io plasma torus.« less

The role of radiative de-excitation in the neutralization process of highly charged ions interacting with a single layer of graphene

NASA Astrophysics Data System (ADS)

Schwestka, J.; Wilhelm, R. A.; Gruber, E.; Heller, R.; Kozubek, R.; Schleberger, M.; Facsko, S.; Aumayr, F.

2018-05-01

X-ray emission of slow (<1 a.u.) highly charged Argon and Xenon ions is measured for transmission through a freestanding single layer of graphene. To discriminate against X-ray emission originating from the graphene's support grid a coincidence technique is used. X-ray emission of 75 keV Ar17+ and Ar18+ ions with either one or two K-shell vacancies is recorded. Using a windowless Bruker XFlash detector allows us to measure additionally Ar KLL and KLM Auger electrons and determine the branching ratio of radiative vs. non-radiative decay of Ar K-shell holes. Furthermore, X-ray spectra for 100 keV Xe22+-Xe35+ ions are compared, showing a broad M-line peak for all cases, where M-shell vacancies are present. All these peaks are accompanied by emission lines at still higher energies indicating the presence of a hollow atom during X-ray decay. We report a linear shift of the main M-line peak to higher energies for increasing incident charge state, i.e. increasing number of M-shell holes.

A temperature, pH and sugar triple-stimuli-responsive nanofluidic diode.

PubMed

Zheng, Yu-Bin; Zhao, Shuang; Cao, Shuo-Hui; Cai, Sheng-Lin; Cai, Xiu-Hong; Li, Yao-Qun

2017-01-07

In this article, we have demonstrated for the first time a triple stimuli-responsive nanofluidic diode that can rectify ionic current under multiple external stimuli including temperature, pH, and sugar. This diode was fabricated by immobilizing poly[2-(dimethylamino)ethyl methacrylate]-co-[4-vinyl phenylboronic acid] (P(DMAEMA-co-VPBA)) onto the wall of a single glass conical nanopore channel via surface-initiator atom transfer radical polymerization (SI-ATRP). The copolymer brushes contain functional groups sensitive to pH, temperature and sugar that can induce charge and configuration change to affect the status of the pore wall. The experimental results confirmed that the P(DMAEMA-co-VPBA) brush modified nanochannel regulated the ionic current rectification successfully under three different external stimuli. This biomimetically inspired research simulates the complex biological multi-functions of ion channels and promotes the development of "smart" biomimetic nanochannel systems for actuating and sensing applications.

Initial Binding of Ions to the Interhelical Loops of Divalent Ion Transporter CorA: Replica Exchange Molecular Dynamics Simulation Study

PubMed Central

Zhang, Tong; Mu, Yuguang

2012-01-01

Crystal structures of Thermotoga maritima magnesium transporter CorA, reported in 2006, revealed its homo-pentameric constructions. However, the structure of the highly conserved extracellular interhelical loops remains unsolved, due to its high flexibility. We have explored the configurations of the loops through extensive replica exchange molecular dynamics simulations in explicit solvent model with the presence of either Co(III) Hexamine ions or Mg2+ ions. We found that there are multiple binding sites available on the interhelical loops in which the negatively charged residues, E316 and E320, are located notably close to the positively charged ions during the simulations. Our simulations resolved the distinct binding patterns of the two kinds of ions: Co(III) Hexamine ions were found to bind stronger with the loop than Mg2+ ions with binding free energy −7.3 kJ/mol lower, which is nicely consistent with the previous data. Our study provides an atomic basis description of the initial binding process of Mg2+ ions on the extracellular interhelical loops of CorA and the detailed inhibition mechanism of Co(III) Hexamine ions on CorA ions transportation. PMID:22952795

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanada, M., E-mail: hanada.masaya@jaea.go.jp; Kojima, A.; Tobari, H.

In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification.more » As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications.« less

Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics

DOE PAGES

Clementson, Joel; Lennartsson, Thomas; Beiersdorfer, Peter

2015-09-09

The extreme ultraviolet (EUV) emission from few-times ionized tungsten atoms has been experimentally studied at the Livermore electron beam ion trap facility. The ions were produced and confined during low-energy operations of the EBIT-I electron beam ion trap. By varying the electron-beam energy from around 30–300 eV, tungsten ions in charge states expected to be abundant in tokamak divertor plasmas were excited, and the resulting EUV emission was studied using a survey spectrometer covering 120–320 Å. It is found that the emission strongly depends on the excitation energy; below 150 eV, it is relatively simple, consisting of strong isolated linesmore » from a few charge states, whereas at higher energies, it becomes very complex. For divertor plasmas with tungsten impurity ions, this emission should prove useful for diagnostics of tungsten flux rates and charge balance, as well as for radiative cooling of the divertor volume. Several lines in the 194–223 Å interval belonging to the spectra of five- and seven-times ionized tungsten (Tm-like W VI and Ho-like W VIII) were also measured using a high-resolution spectrometer.« less

Thermodynamics of various F420 coenzyme models as sources of electrons, hydride ions, hydrogen atoms and protons in acetonitrile.

PubMed

Xia, Ke; Shen, Guang-Bin; Zhu, Xiao-Qing

2015-06-14

32 F420 coenzyme models with alkylation of the three different N atoms (N1, N3 and N10) in the core structure (XFH(-)) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH(-) releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF(-)˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N1, N3 and N10 and a negative charge on N1 and N10 atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C7 and C8 on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C7 and C8 have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH(-) and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme.

Ion-atom charge-transfer reactions and a hot intercloud medium. [in interstellar space

NASA Technical Reports Server (NTRS)

Steigman, G.

1975-01-01

An investigation is conducted concerning the ionization equilibrium of carbon in a hot intercloud medium (ICM), taking into account various charge-transfer reactions. Attention is given to problems related to observations of carbon along the lines of sight to several unreddened stars. It is pointed out that the observed underabundance of C III and overabundance of C I can be consistent with the presence of a hot, partially ionized ICM, provided that two of the charge-transfer reactions considered are rapid at thermal energies.

Energy-transfer processes in neon-hydrogen mixtures excited by electron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morozov, A.; Kruecken, R.; Ulrich, A.

2005-12-15

Energy- and charge-transfer processes in neon-hydrogen mixtures (500-1400 hPa neon and 0.001-3 hPa hydrogen partial pressures) excited by a pulsed low-energy ({approx}10 keV) electron beam were investigated using time-resolved spectroscopy. Time spectra of the hydrogen Lyman-{alpha} line, neon excimer emission (second continuum), and neon atomic lines (3p-3s transitions) were recorded. The time-integrated intensity of the Lyman-{alpha} emission was measured for the same range of gas mixtures. It is shown that direct energy transfer from Ne{sub 2}* excimers and neon atoms in the four lowest excited states as well as recombination of H{sub 3}{sup +} ions are the main channels populatingmore » atomic hydrogen in the n=2 state. A rate constant of (4.2{+-}1.4)x10{sup -11} cm{sup 3} s{sup -1} was obtained for the charge transfer from Ne{sub 2}{sup +} ions to molecular hydrogen. A lower limit for the depopulation rate constant of Ne{sub 2}* excimers by molecular hydrogen (combination of energy transfer and ionization) was found to be 1.0x10{sup -10} cm{sup 3} s{sup -1}.« less

Charge equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1979-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, are considered. Electron loss of the beam has been taken into account by means of the first Born approximation, allowing for the target atom to remain unexcited or to be excited to all possible states. Electron-capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms and capture into all excited states of the projectile. The capture and loss cross sections are found to be within 20%-30% of the existing experimental values for most of the cases considered. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation, and collisional inner-shell ionization, taking into account the fluorescence yield of the ions, has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated, and error estimates made for the results.

Electronic structure, bonding, charge distribution, and x-ray absorption spectra of the (001) surfaces of fluorapatite and hydroxyapatite from first principles

NASA Astrophysics Data System (ADS)

Rulis, Paul; Yao, Hongzhi; Ouyang, Lizhi; Ching, W. Y.

2007-12-01

Fluorapatite (FAP) and hydroxyapatite (HAP) are two very important bioceramic crystals. The (001) surfaces of FAP and HAP crystals are studied by ab initio density functional calculations using a supercell slab geometry. It is shown that in both crystals, the O-terminated (001) surface is more stable with calculated surface energies of 0.865 and 0.871J/m2 for FAP and HAP, respectively. In FAP, the two surfaces are symmetric. In HAP, the orientation of the OH group along the c axis reduces the symmetry such that the top and bottom surfaces are no longer symmetric. It is revealed that the atoms near the surface and subsurface are significantly relaxed especially in the case of HAP. The largest relaxations occurred via the lateral movements of the O ions at the subsurface level. The electronic structures of the surface models in the form of layer-by-layer resolved partial density of states for all the atoms show systematic variation from the surface region toward the bulk region. The calculated Mulliken effective charge on each type of atom and the bond order values between cations (Ca, P) and anions (O, F) show different charge transfers and bond strength variations from the bulk crystal values. Electron charge density calculations show that the surfaces of both FAP and HAP crystals are mostly positively charged due to the presence of Ca ions at the surface. The positively charged surfaces have implications for the absorption on apatite surfaces of water and other organic molecules in an aqueous environment which are an important part of its bioactivity. The x-ray absorption near-edge structure (XANES) spectra ( Ca-K , O-K , F-K , P-K , and P-L3 edges) of both the surface models and the bulk crystals are calculated and compared. The calculations use a supercell approach which takes into account the electron-core-hole interaction. It is shown that the site-specific XANES spectra show significant differences between atoms near the surface and in the bulk and are very sensitive to the local atomic environment of each atom. This information will be very valuable for characterizing the apatite materials and in the interpretation of experimental data. Comparisons of several sets of experimental data with the weighted sums of the calculated spectra at different sites for the same element show very good agreement.

Influence of inelastic Rydberg atom-atom collisional process on kinetic and optical properties of low-temperature laboratory and astrophysical plasmas

NASA Astrophysics Data System (ADS)

Klyucharev, A. N.; Bezuglov, N. N.; Mihajlov, A. A.; Ignjatović, Lj M.

2010-11-01

Elementary processes in plasma phenomena traditionally attract physicist's attention. The channel of charged-particle formation in Rydberg atom-atom thermal and sub-thermal collisions (the low temperature plasmas conditions) leads to creation of the molecular ions - associative ionization (AI). atomic ions - Penning-like ionization (PI) and the pair of the negative and positive ions. In our universe the chemical composition of the primordial gas consists mainly of Hydrogen and Helium (H, H-, H+, H2, He,He+). Hydrogen-like alkali-metal Lithium (Li, Li+,Li-) and combinations (HeH+, LiH-, LiH+). There is a wide range of plasma parameters in which the Rydberg atoms of the elements mentioned above make the dominant contribution to ionization and that process may be regarded as a prototype of the elementary process of light excitation energy transformation into electric one. The latest stochastic version of chemi-ionisation (AI+PI) on Rydberg atom-atom collisions extends the treatment of the "dipole resonant" model by taking into account redistribution of population over a range of Rydberg states prior to ionization. This redistribution is modelled as diffusion within the frame of stochastic dynamic of the Rydberg electron in the Rydberg energy spectrum. This may lead to anomalies of Rydberg atom spectra. Another result obtained in recent time is understanding that experimental results on chemi-ionization relate to the group of mixed Rydberg atom closed to the primary selected one. The Rydberg atoms ionisation theory today makes a valuable contribution in the deterministic and stochastic approaches correlation in atomic physic.

A New Method of Estimating Atomic Charges by Electronegativity Equilibration.

ERIC Educational Resources Information Center

Smith, Derek W.

1990-01-01

Presented is a modification of Bratsch's prescription so that difficult problems are obviated while simple, familiar Pauling electronegativities are retained. Discussed are the equilibration of electronegativity in molecules, group electronegativities, coordination compounds and molecules with dative bonds, ions, and correlation with core…

Recent Livermore Excitation and Dielectronic Recombination Measurements for Laboratory and Astrophysical Spectral Modeling

NASA Technical Reports Server (NTRS)

Beiersdorfer, P.; Brown, G. V.; Gu, M.-F.; Harris, C. L.; Kahn, S. M.; Kim, S.-H.; Neill, P. A.; Savin, D. W.; Smith, A. J.; Utter, S. B.

2000-01-01

Using the EBIT facility in Livermore we produce definitive atomic data for input into spectral synthesis codes. Recent measurements of line excitation and dielectronic recombination of highly charged K-shell and L-shell ions are presented to illustrate this point.

Compact, accurate description of diagnostic neutral beam propagation and attenuation in a high temperature plasma for charge exchange recombination spectroscopy analysis.

PubMed

Bespamyatnov, Igor O; Rowan, William L; Granetz, Robert S

2008-10-01

Charge exchange recombination spectroscopy on Alcator C-Mod relies on the use of the diagnostic neutral beam injector as a source of neutral particles which penetrate deep into the plasma. It employs the emission resulting from the interaction of the beam atoms with fully ionized impurity ions. To interpret the emission from a given point in the plasma as the density of emitting impurity ions, the density of beam atoms must be known. Here, an analysis of beam propagation is described which yields the beam density profile throughout the beam trajectory from the neutral beam injector to the core of the plasma. The analysis includes the effects of beam formation, attenuation in the neutral gas surrounding the plasma, and attenuation in the plasma. In the course of this work, a numerical simulation and an analytical approximation for beam divergence are developed. The description is made sufficiently compact to yield accurate results in a time consistent with between-shot analysis.

Complexes of carboxyl-containing polymer and monosubstituted bipyridinium salts

NASA Astrophysics Data System (ADS)

Merekalova, N. D.; Bondarenko, G. N.; Krylsky, D. W.; Zakirov, M. I.; Talroze, R. V.

2013-09-01

Semi-empirical PM3 method for the quantum calculations of molecular electronic structure based on NDDO integral approximation is used to investigate the complex formation of monosubstituted 4,4‧-bipyridinium salts BpyR (Hal) containing a halide anion interacting with the quaternary nitrogen atom and carboxylic group of the two-units construct. Significant effect of the BpyR (Hal) electronic structure is unveiled that contributes in two different structures of these salts, namely, partial charge transfer complex and ion pair structure, both having stable energy minima. We demonstrate that (i) the structure of the N-substituent modulates the energy and electronic characteristics of monosubstituted salts BpyR with chlorine and bromine anions and (ii) the coulomb interactions between quaternary N-atom, halogen anion, and the proton of carboxylic group stimulate the transformation of the charge transfer complex into the ion pair structure. Results of calculations are compared with the experimental FTIR spectra of blends of BpyR(Hal) with Eudragit copolymer.

Colloquium: Laser probing of neutron-rich nuclei in light atoms

NASA Astrophysics Data System (ADS)

Lu, Z.-T.; Mueller, P.; Drake, G. W. F.; Nörtershäuser, W.; Pieper, Steven C.; Yan, Z.-C.

2013-10-01

The neutron-rich He6 and He8 isotopes exhibit an exotic nuclear structure that consists of a tightly bound He4-like core with additional neutrons orbiting at a relatively large distance, forming a halo. Recent experimental efforts have succeeded in laser trapping and cooling these short-lived, rare helium atoms and have measured the atomic isotope shifts along the He4-He6-He8 chain by performing laser spectroscopy on individual trapped atoms. Meanwhile, the few-electron atomic structure theory, including relativistic and QED corrections, has reached a comparable degree of accuracy in the calculation of the isotope shifts. In parallel efforts, also by measuring atomic isotope shifts, the nuclear charge radii of lithium and beryllium isotopes have been studied. The techniques employed were resonance ionization spectroscopy on neutral, thermal lithium atoms and collinear laser spectroscopy on beryllium ions. Combining advances in both atomic theory and laser spectroscopy, the charge radii of these light halo nuclei have now been determined for the first time independent of nuclear structure models. The results are compared with the values predicted by a number of nuclear structure calculations and are used to guide our understanding of the nuclear forces in the extremely neutron-rich environment.

Method of precisely modifying predetermined surface layers of a workpiece by cluster ion impact therewith

DOEpatents

Friedman, L.; Beuhler, R.J.; Matthew, M.W.; Ledbetter, M.

1984-06-25

A method of precisely modifying a selected area of a workpiece by producing a beam of charged cluster ions that is narrowly mass selected to a predetermined mean size of cluster ions within a range of 25 to 10/sup 6/ atoms per cluster ion, and accelerated in a beam to a critical velocity. The accelerated beam is used to impact a selected area of an outer surface of the workpiece at a preselected rate of impacts of cluster ions/cm/sup 2//sec in order to effect a precise modification in that selected area of the workpiece.

Method of precisely modifying predetermined surface layers of a workpiece by cluster ion impact therewith

DOEpatents

Friedman, Lewis; Buehler, Robert J.; Matthew, Michael W.; Ledbetter, Myron

1985-01-01

A method of precisely modifying a selected area of a workpiece by producing a beam of charged cluster ions that is narrowly mass selected to a predetermined mean size of cluster ions within a range of 25 to 10.sup.6 atoms per cluster ion, and accelerated in a beam to a critical velocity. The accelerated beam is used to impact a selected area of an outer surface of the workpiece at a preselected rate of impacts of cluster ions/cm.sup.2 /sec. in order to effect a precise modification in that selected area of the workpiece.

Geoengineering with Charged Droplets

NASA Astrophysics Data System (ADS)

Gokturk, H.

2011-12-01

Water molecules in a droplet are held together by intermolecular forces generated by hydrogen bonding which has a bonding energy of only about 0.2 eV. One can create a more rugged droplet by using an ion as a condensation nucleus. In that case, water molecules are held together by the interaction between the ion and the dipole moments of the water molecules surrounding the ion, in addition to any hydrogen bonding. In this research, properties of such charged droplets were investigated using first principle quantum mechanical calculations. A molecule which exhibits positive electron affinity is a good candidate to serve as the ionic condensation nucleus, because addition of an electron to such a molecule creates an energetically more stable state than the neutral molecule. A good example is the oxygen molecule (O2) where energy of O2 negative (O2-) ion is lower than that of the neutral O2 by about 0.5 eV. Examples of other molecules which have positive electron affinity include ozone (O3), nitrogen dioxide (NO2) and sulfur oxides (SOx, x=1-3). Atomic models used in the calculations consisted of a negative ion of one of the molecules mentioned above surrounded by water molecules. Calculations were performed using the DFT method with B3LYP hybrid functional and Pople type basis sets with polarization and diffuse functions. Energy of interaction between O2- ion and the water molecule was found to be ~0.7 eV. This energy is an order of magnitude greater than the thermal energy of even the highest temperatures encountered in the atmosphere. Once created, charged rugged droplets can survive in hot and dry climates where they can be utilized to create humidity and precipitation. The ion which serves as the nucleus of the droplet can attract not only water molecules but also other dipolar gases in the atmosphere. Such dipolar gases include industrial pollutants, for example nitrogen dioxide (NO2) or sulfur dioxide (SO2). Energy of interaction between O2- ion and pollutant molecules was calculated to be ~0.5 eV for NO2 and ~0.9 eV for SO2. These values are comparable to that of water, hence charged droplets have the potential to serve as scavengers of pollutants in the atmosphere. The charged droplet can also interact with quadrupolar gases depending on the charge distribution of the gas. A quadrupole of interest is carbon dioxide (CO2) where oxygens are slightly negative and carbon is slightly positive in a neutral molecule. When CO2 is in the vicinity of a negative ion, the carbon atom gets attracted to the ion, whereas oxygens are repelled from it. This interaction distorts the linear geometry of CO2, turning it into a small dipole. Energy of interaction between O2- ion and CO2 was calculated to be ~0.3 eV which is smaller than those of the above mentioned dipoles, but still significantly greater than the typical thermal energy at 25 C (~0.03 eV). One can expect the diffusion of atmospheric CO2 into the droplets to be enhanced due to the charge. Hence such droplets can help capture the CO2 in the atmosphere and sequester it simply as rain. Charged droplets can be created using electrical,optical, thermal or other means. A method which utilizes solar energy will be described in the presentation.

IBEX-Lo Observations of Secondary Interstellar Helium and Oxygen Distributions

NASA Astrophysics Data System (ADS)

Park, J.; Kucharek, H.; Moebius, E.; Kubiak, M. A.; Bzowski, M.; Galli, A.; McComas, D. J.

2015-12-01

Observations of the Interstellar Boundary EXplorer (IBEX) show, among other features, the pristine interstellar neutral gas flow and additional populations associated with neutral helium and oxygen. Kubiak et al. (2014, ApJS, 213, 29) discovered the "Warm Breeze", or additional He component, which is slower and warmer than the primary interstellar He population and its flow direction differs by about 19° from the interstellar neutral (ISN) flow. Park et al. (2015, ApJS, In Press) studied the combined count rate maps of heavy neutral atoms with three statistical analysis methods and found an extended tail of the ISN O flow, centered around 190° in ecliptic longitude and +15° in ecliptic latitude, or approximately 38° from the ISN O and Ne flow peak. The most likely sources for the Warm Breeze and the extended O tail may be secondary populations of interstellar He and O, created by charge exchange between ISN atoms and interstellar ions in the outer heliosheath. The charge exchange between interstellar He atoms and He+ ions is the most important reaction to generate the secondary neutral He in the outer heliosheath, with a reaction rate of 1.7×10-10 s-1 and a mean free path of ~950 AU. For O+, the charge exchange with interstellar H atoms with a rate ~1.0×10-9 s-1 and a mean free path of ~100 AU is most important. Because the differences in the reaction rates and atomic masses for He and O result in different velocity distributions in the outer heliosheath, the directional distributions of these populations at Earth orbit are not identical. In this study, we use the IBEX flux maps of the observed helium and oxygen atoms to compare their directional distributions. These observed distributions may provide constraints and information to improve our current understanding of the interactions in the outer heliosheath.

New Radiation Zones on Jupiter

NASA Image and Video Library

2017-12-11

This graphic shows a new radiation zone surrounding Jupiter, located just above the atmosphere near the equator, that has been discovered by NASA's Juno mission. The new radiation zone is depicted here as a glowing blue area around the planet's middle. This radiation zone includes energetic hydrogen, oxygen and sulfur ions moving at close to the speed of light (referred to as "relativistic" speeds). It resides inside Jupiter's previously known radiation belts. The zone was identified by the mission's Jupiter Energetic Particle Detector Instrument (JEDI), enabled by Juno's unique close approach to the planet during the spacecraft's science flybys (2,100 miles or 3,400 kilometers from the cloud tops). Juno scientists believe the particles creating this region of intense radiation are derived from energetic neutral atoms -- that is, fast-moving atoms without an electric charge -- coming from the tenuous gas around Jupiter's moons Io and Europa. The neutral atoms then become ions -- atoms with an electric charge -- as their electrons are stripped away by interaction with the planet's upper atmosphere. (This discovery is discussed further in an issue of the journal Geophysical Research Letters [Kollmann et al. (2017), Geophys. Res. Lett., 44, 5259-5268].) Juno also has detected signatures of a population of high-energy, heavy ions in the inner edges of Jupiter's relativistic electron radiation belt. This radiation belt was previously understood to contain mostly electrons moving at near light speed. The signatures of the heavy ions are observed at high latitude locations within the electron belt -- a region not previously explored by spacecraft. The origin and exact species of these heavy ions is not yet understood. Juno's Stellar Reference Unit (SRU-1) star camera detects the signatures of this population as extremely high noise in images collected as part of the mission's radiation monitoring investigation. The locations where the heavy ions were detected are indicated on the graphic by two bright, glowing spots along Juno's flight path past the planet, which is shown as a white line. The invisible lines of Jupiter's magnetic field are also portrayed here for context as faint, bluish lines. https://photojournal.jpl.nasa.gov/catalog/PIA22179

Charge Transfer in Collisions of S^4+ with H.

NASA Astrophysics Data System (ADS)

Stancil, P. C.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Zygelman, B.

2001-05-01

Charge transfer processes due to collisions of ground state S^4+ ions with atomic hydrogen were investigated for energies between 1 meV/u and 10 MeV/u using the quantum-mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC), and continuum distorted wave methods. The MOCC calculations utilized ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially-stripped S^3+ excited classical states. Hydrogen target isotope effects were explored and rate coefficients for temperatures between 100 and 10^6 K will be presented

Closed-form expressions for state-to-state charge-transfer differential cross sections in a modified Faddeev three-body approach

NASA Astrophysics Data System (ADS)

Adivi, E. Ghanbari; Brunger, M. J.; Bolorizadeh, M. A.; Campbell, L.

2007-02-01

The second-order Faddeev-Watson-Lovelace approximation in a modified form is applied to charge transfer from hydrogenlike target atoms by a fully stripped energetic projectile ion. The state-to-state, nlm→n'l'm' , partial transition amplitudes are calculated analytically. The method is specifically applied to the collision of protons with hydrogen atoms, where differential cross sections of different transitions are calculated for incident energies of 2.8 and 5.0MeV . It is shown that the Thomas peak is present in all transition cross sections. The partial cross sections are then summed and compared with the available forward-angle experimental data, showing good agreement.

Soft Landing of Mass-Selected Gold Clusters: Influence of Ion and Ligand on Charge Retention and Reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Grant E.; Laskin, Julia

Herein, we employ a combination of reduction synthesis in solution, soft landing of mass-selected precursor and product ions, and in situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) to examine the influence of ion and the length of diphosphine ligands on the charge retention and reactivity of ligated gold clusters deposited onto self-assembled monolayer surfaces (SAMs). Product ions (Au10L42+, (10,4)2+, L = 1,3-bis(diphenyl-phosphino)propane, DPPP) were prepared through in-source collision induced dissociation (CID) and precursor ions [(8,4)2+, L = 1,6-bis(diphenylphosphino)hexane, DPPH] were synthesized in solution for comparison to (11,5)3+ precursor ions ligated with DPPP investigated previously (ACS Nano 2012, 6, 573 andmore » J. Phys. Chem. C. 2012, 116, 24977). Similar to (11,5)3+ precursor ions, the (10,4)2+ product ions are shown to retain charge on 1H,1H,2H,2H-perfluorodecanethiol monolayers (FSAMs). Additional abundant peaks at higher m/z indicative of reactivity are observed in the TOF-SIMS spectrum of (10,4)2+ product ions that are not seen for (11,5)3+ precursor ions. The abundance of (10,4)2+ on 16-mercaptohexadecanoic acid (COOH-SAMs) is demonstrated to be lower than on FSAMs, consistent with partial reduction of charge. The (10,4)2+ product ion on 1-dodecanethiol (HSAMs) exhibits peaks similar to those seen on the COOH-SAM. On the HSAM, higher m/z peaks indicative of reactivity are observed similar to those on the FSAM. The (8,4)2+ DPPH precursor ions are shown to retain charge on FSAMs similar to (11,5)3+ precursor ions prepared with DPPP. An additional peak corresponding to attachment of one gold atom to (8,4)2+ is observed at higher m/z for DPPH-ligated clusters. On the COOH-SAM, (8,4)2+ is less abundant than on the FSAM consistent with partial neutralization. The results indicate that although retention of charge by product ions generated by CID is similar to precursor ions their reactivity during analysis with SIMS is different resulting in the formation of peaks corresponding to reaction products. The length of the ligand exerts only a minor influence on the charge retention and reactivity of gold clusters. Based on the observed reactivity of (10,4)2+ it is anticipated that in-source CID will be increasingly applied for the preparation of a distribution of product ions, including undercoordinated and reactive species, for soft landing onto surfaces.« less

Effect of giant charge-transfer resonance σCT 109 barn on operation of magnetic fusion reactor below ``critical energy.''

NASA Astrophysics Data System (ADS)

Hester, Timothy; Maglich, Bogdan; Scott, Dan; Vaucher, Alexander

2016-10-01

Charge transfer (CT) reactivity was assumed to be negligible compared to ionization (IO) before Belfast measurements1-3 revealed the opposite: CT predominance over IO, σCT 109 b , σCT /σIO U 100 , below critical `atomic unit of velocity', vo = 2.2 ×108cms-1 , which is orbital velocity of e in H atom. Near vo, U = 1 , i.e. σCT σIO . Critical ion energy is T0 (lab) = k 25 M [ KeV ] = 200 KeV for [ ERR : md : MbegChr = 0 x 2329 , MendChr = 0 x 232 A , nParams = 1 ] = ion mass [ amu ] = 4 for DT mix ; k = 2 . ``Burnout'' pumping that requires U << 1 is inoperable in the U >> 1 regime whereas CT continually acts like compressor increasing operating vacuum pressure during neutral beam discharge to 10-3 Torr/0.3 s; this, in turn, sets upper limits to ion life-time against neutralization to τ =10-6 s. τ is 105 times shorter than thermalization time constant; hence plasma cannot be created. Lawson4 was unaware of CT resonance; his ``critical temperature'' (30 KeV for DT) should be replaced with T0.

Nanosecond laser-cluster interactions at 109-1012 W/cm 2

NASA Astrophysics Data System (ADS)

Singh, Rohtash; Tripathi, V. K.; Vatsa, R. K.; Das, D.

2017-08-01

An analytical model and a numerical code are developed to study the evolution of multiple charge states of ions by irradiating clusters of atoms of a high atomic number (e.g., Xe) by 1.06 μm and 0.53 μm nanosecond laser pulses of an intensity in the range of 109-1012 W/cm 2 . The laser turns clusters into plasma nanoballs. Initially, the momentum randomizing collisions of electrons are with neutrals, but soon these are taken over by collisions with ions. The ionization of an ion to the next higher state of ionization is taken to be caused by an energetic free electron impact, and the rates of impact ionization are suitably modelled by having an inverse exponential dependence of ionizing collision frequency on the ratio of ionization potential to electron temperature. Cluster expansion led adiabatic cooling is a major limiting mechanism on electron temperature. In the intensity range considered, ionization states up to 7 are expected with nanosecond pulses. Another possible mechanism, filamentation of the laser, has also been considered to account for the observation of higher charged states. However, filamentation is seen to be insufficient to cause substantial local enhancement in the intensity to affect electron heating rates.

Analysis of unresolved transition arrays in XUV spectral region from highly charged lead ions produced by subnanosecond laser pulse

NASA Astrophysics Data System (ADS)

Wu, Tao; Higashiguchi, Takeshi; Li, Bowen; Arai, Goki; Hara, Hiroyuki; Kondo, Yoshiki; Miyazaki, Takanori; Dinh, Thanh-Hung; O'Reilly, Fergal; Sokell, Emma; O'Sullivan, Gerry

2017-02-01

Soft x-ray and extreme ultraviolet (XUV) spectra from lead (Pb, Z=82) laser-produced plasmas (LPPs) were measured in the 1.0-7.0 nm wavelength region employing a 150-ps, 1064-nm Nd:YAG laser with focused power densities in the range from 3.1×1013 W/cm2 to 1.4×1014 W/cm2. The flexible atomic code (FAC) and the Cowan's suite of atomic structure codes were applied to compute and explain the radiation properties of the lead spectra observed. The most prominent structure in the spectra is a broad double peak, which is produced by Δn=0, n=4-4 and Δn=1, n=4-5 transition arrays emitted from highly charged lead ions. The emission characteristics of Δn=1, n=4-5 transitions were investigated by the use of the unresolved transition arrays (UTAs) model. Numerous new spectral features generated by Δn=1, n=4-5 transitions in ions from Pb21+ to Pb45+ are discerned with the aid of the results from present computations as well as consideration of previous theoretical predictions and experimental data.

Reconstructing Ion Spectra from Low-Altitude ENAs: Moderate to Large Storms.

NASA Astrophysics Data System (ADS)

LLera, K.; Goldstein, J.; McComas, D. J.; Valek, P. W.

2015-12-01

Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) Energetic neutral atom (ENA) imagers regularly observe Low-altitude Emission (LAE) intensifications during geomagnetic storm intervals. Since LAEs are produced by the interaction between ions and the near-Earth exosphere (altitudes ~200-800 km), they are a global signature of how the ring current decays in response to solar wind conditions. In this "optically thick" region, an ENA readily becomes reionized, and an ion is readily neutralized. Therefore, emerging ENAs that contribute to the LAE signal (detectable several RE away) have undergone multiple charge exchange and electron stripping interactions. Accounting for the ~36 eV energy loss per interaction, we developed a model to quantify the total energy lost by emergent LAEs. The analytical tool is applied to an ensemble of moderate to large storms (including the recent 17 March and 23 June storms in 2015) to reconstruct the parent ion spectra from TWINS ENA images. We examine the ion spectra energy characteristics among the various storm events.

Advances in Charge-Compensation in Secondary Ion Mass Spectrometry (SIMS)

NASA Astrophysics Data System (ADS)

Hervig, R. L.; Chen, J.; Schauer, S.; Stanley, B. D.; Moore, G. M.; Roggensack, K.

2012-12-01

In secondary ion mass spectrometry (SIMS), a sample is bombarded by a charged particle beam (the primary ion) and sputtered positive or negative secondary ions are analyzed in a mass spectrometer. When the target is not conducting (like many geological materials), sample charging can result in variable deflection of secondary ions away from the mass spectrometer and a low, unstable, or absent signal. Applying a thin conducting coat (e.g., C, Au) to polished samples is required, and if the primary ion beam is negatively-charged, the build-up of negative charge can be alleviated by secondary electrons draining to the conducting coat at the edge of the crater (if a positive potential is applied to the sample for the collection of positive secondary ions) or accelerated away from the crater (if a negative potential is applied for negative ion study). Unless the sputtered crater in the conducting coat becomes too large, sample charging can be kept at a controllable level, and high-quality trace element analyses and isotope ratios have been obtained using this technique over the past 3+ decades. When a positive primary beam is used, the resulting build-up of positive charge in the sample requires an electron gun to deliver sufficient negative charge to the sputtered crater. While there are many examples of successful analyses using this approach, the purpose of this presentation is to describe a very simple technique for aligning the electron gun on Cameca nf and 1270/80 SIMS instruments. This method allows reproducible analyses of insulating phases with a Cs+ primary beam and detection of negative secondary ions. Normally, the filament voltage on the E-gun is the same as the sample voltage; thus electrons do not strike the sample except when a positive charge has built up (e.g., in the analysis crater!). In this method, we decrease the sample voltage by 3 or more kV, so that the impact energy of the electrons is sufficient to induce a cathodoluminescent (CL) image on an appropriate sample (e.g., GaN). The CL image is made circular and homogeneous by adjusting the deflectors and a lens in the electron steering assembly, and the sample voltage is subsequently returned to the same value as the filament. Very minor corrections of the electron tuning (mostly by an external magnet known as Bx or B1) will then produce a uniform secondary ion image on a test insulator (a gold-coated glass slide) under Cs bombardment. The uniform electron density is correlated with reproducible calibration for hydrogen and carbon concentrations over a multi-day session and from session to session over a period of months. Outside visitors to the lab can use this set-up and obtain high-quality analyses with little to no previous training. Obtaining a homogeneous distribution of electrons over a maximum diameter (100+ microns) also reduces problems associated with changes in the position of the electron beam induced by stray magnetic fields. As a result, analyses of hydrogen isotopes and/or multi-element analysis routines using elemental H species are simplified.

Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

PubMed

Petrović, Z Lj; Phelps, A V

2009-12-01

Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4

Identifying the elusive link between amino acid sequence and charge selectivity in pentameric ligand-gated ion channels.

PubMed

Cymes, Gisela D; Grosman, Claudio

2016-10-10

Among neurotransmitter-gated ion channels, the superfamily of pentameric ligand-gated ion channels (pLGICs) is unique in that its members display opposite permeant-ion charge selectivities despite sharing the same structural fold. Although much effort has been devoted to the identification of the mechanism underlying the cation-versus-anion selectivity of these channels, a careful analysis of past work reveals that discrepancies exist, that different explanations for the same phenomenon have often been put forth, and that no consensus view has yet been reached. To elucidate the molecular basis of charge selectivity for the superfamily as a whole, we performed extensive mutagenesis and electrophysiological recordings on six different cation-selective and anion-selective homologs from vertebrate, invertebrate, and bacterial origin. We present compelling evidence for the critical involvement of ionized side chains-whether pore-facing or buried-rather than backbone atoms and propose a mechanism whereby not only their charge sign but also their conformation determines charge selectivity. Insertions, deletions, and residue-to-residue mutations involving nonionizable residues in the intracellular end of the pore seem to affect charge selectivity by changing the rotamer preferences of the ionized side chains in the first turn of the M2 α-helices. We also found that, upon neutralization of the charged residues in the first turn of M2, the control of charge selectivity is handed over to the many other ionized side chains that decorate the pore. This explains the long-standing puzzle as to why the neutralization of the intracellular-mouth glutamates affects charge selectivity to markedly different extents in different cation-selective pLGICs.

Electron- and Photon-stimulated Desorption of Alkali Atoms from Lunar Sample and a Model Mineral Surface

NASA Technical Reports Server (NTRS)

Yakshinskiy, B. V.; Madey, T. E.

2003-01-01

We report recent results on an investigation of source mechanisms for the origin of alkali atoms in the tenuous planetary atmospheres, with focus on non-thermal processes (photon stimulated desorption (PSD), electron stimulated desorption (ESD), and ion sputtering). Whereas alkaline earth oxides (MgO, CaO) are far more abundant in lunar samples than alkali oxides (Na2O, K2O), the atmosphere of the Moon contains easily measurable concentrations of Na and K, while Ca and Mg are undetected there; traces of Ca have recently been seen in the Moon's atmosphere (10-3 of Na). The experiments have included ESD, PSD and ion sputtering of alkali atoms from model mineral surface (amorphous SiO2) and from a lunar basalt sample obtained from NASA. The comparison is made between ESD and PSD efficiency of monovalent alkalis (Na, K) and divalent alkaline earths (Ba, Ca).The ultrahigh vacuum measurement scheme for ESD and PSD of Na atoms includes a highly sensitive alkali metal detector based on surface ionization, and a time-of-flight technique. For PSD measurements, a mercury arc light source (filtered and chopped) is used. We find that bombardment of the alkali covered surfaces by ultraviolet photons or by low energy electrons (E>4 eV) causes desorption of hot alkali atoms. This results are consistent with the model developed to explain our previous measurements of sodium desorption from a silica surface and from water ice: electron- or photon-induced charge transfer from the substrate to the ionic adsorbate causes formation of a neutral alkali atom in a repulsive configuration, from which desorption occurs. The two-electron charge transfer to cause desorption of divalent alkaline eath ions is a less likely process.The data support the suggestion that PSD by UV solar photons is a dominant source process for alkalis in the tenuous lunar atmosphere.

Ion-Atom Cold Collisions and Atomic Clocks

NASA Technical Reports Server (NTRS)

Prestage, John D.; Maleki, Lute; Tjoelker, Robert L.

1997-01-01

Collisions between ultracold neutral atoms have for some time been the subject of investigation, initially with hydrogen and more recently with laser cooled alkali atoms. Advances in laser cooling and trapping of neutral atoms in a Magneto-Optic Trap (MOT) have made cold atoms available as the starting point for many laser cooled atomic physics investigations. The most spectacularly successful of these, the observation of Bose-Einstein Condensation (BEC) in a dilute ultra-cold spin polarized atomic vapor, has accelerated the study of cold collisions. Experimental and theoretical studies of BEC and the long range interaction between cold alkali atoms is at the boundary of atomic and low temperature physics. Such studies have been difficult and would not have been possible without the development and advancement of laser cooling and trapping of neutral atoms. By contrast, ion-atom interactions at low temperature, also very difficult to study prior to modern day laser cooling, have remained largely unexplored. But now, many laboratories worldwide have almost routine access to cold neutral atoms. The combined technologies of ion trapping, together with laser cooling of neutrals has made these studies experimentally feasible and several very important, novel applications might come out of such investigations . This paper is an investigation of ion-atom interactions in the cold and ultra-cold temperature regime. Some of the collisional ion-atom interactions present at room temperature are very much reduced in the low temperature regime. Reaction rates for charge transfer between unlike atoms, A + B(+) approaches A(+) + B, are expected to fall rapidly with temperature, approximately as T(sup 5/2). Thus, cold mixtures of atoms and ions are expected to coexist for very long times, unlike room temperature mixtures of the same ion-atom combination. Thus, it seems feasible to cool ions via collisions with laser cooled atoms. Many of the conventional collisional interactions, exploited as a useful tool at room temperature and higher, are greatly enhanced at low energy. For example, collisional spin transfer from one species of polarized atoms to another has long been a useful method for polarizing a sample of atoms where no other means was available. Because optical pumping cannot be used to polarize the nuclear spin of Xe-129 or He-3 (for use in nmr imaging of the lungs), the nuclear spins are polarized via collisions with an optically pumped Rb vapor in a cell containing both gases. In another case, a spin polarized thermal Cs beam was used to polarize the hyperfine states of trapped He(+)-3 ions in order to measure their hyperfine clock transition frequency. The absence of an x-ray light source to optically pump the ground state of the He(+)-3 ion necessitated this alternative state preparation. Similarly, Cd(+) and Sr(+) ions were spin-oriented via collisions in a cell with optically pumped Rb vapor. Resonant RF spin changing transitions in the ground state of the ions were detected by changes in the Rb resonance light absorption. Because cold collision spin exchange rates scale with temperature as T(sup -1/2) this technique is expected to be a far more powerful tool than the room temperature counterpart. This factor of 100 or more enhancement in spin exchange reaction rates at low temperatures is the basis for a novel trapped ion clock where laser cooled neutrals will cool, state select and monitor the ion clock transition. The advantage over conventional direct laser cooling of trapped ions is that the very expensive and cumbersome UV laser light sources, required to excite the ionic cooling transition, are effectively replaced by simple diode lasers.

The role of highly oxygenated molecules (HOMs) in determining the composition of ambient ions in the boreal forest

NASA Astrophysics Data System (ADS)

Bianchi, Federico; Garmash, Olga; He, Xucheng; Yan, Chao; Iyer, Siddharth; Rosendahl, Ida; Xu, Zhengning; Rissanen, Matti P.; Riva, Matthieu; Taipale, Risto; Sarnela, Nina; Petäjä, Tuukka; Worsnop, Douglas R.; Kulmala, Markku; Ehn, Mikael; Junninen, Heikki

2017-11-01

In order to investigate the negative ions in the boreal forest we have performed measurements to chemically characterise the composition of negatively charged clusters containing highly oxygenated molecules (HOMs). Additionally, we compared this information with the chemical composition of the neutral gas-phase molecules detected in the ambient atmosphere during the same period. The chemical composition of the ions was retrieved using an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF-MS) while the gas-phase neutral molecules (mainly sulfuric acid and HOMs) were characterised using the same mass spectrometer coupled to a nitrate-based chemical ionisation unit (CI-APi-TOF). Overall, we divided the identified HOMs in two classes: HOMs containing only carbon, hydrogen and oxygen and nitrogen-containing HOMs or organonitrates (ONs). During the day, among the ions, in addition to the well-known pure sulfuric acid clusters, we found a large number of HOMs clustered with nitrate (NO3-) or bisulfate (HSO4-), with the first one being more abundant. During the night, the distribution of ions, mainly composed of HOM clustered with NO3-, was very similar to the neutral compounds that are detected in the CI-APi-TOF as adducts with the artificially introduced primary ion (NO3-). For the first time, we identified several clusters containing up to 40 carbon atoms. These ions are formed by up to four oxidised α-pinene units clustered with NO3-. While we know that dimers (16-20 carbon atoms) are probably formed by a covalent bond between two α-pinene oxidised units, it is still unclear what bonding formed larger clusters. Finally, diurnal profiles of the negative ions were consistent with the neutral compounds revealing that ONs peak during the day while HOMs are more abundant at night-time. However, during the day, a large fraction of the negative charge is taken up by the pure sulfuric acid clusters causing differences between ambient ions and neutral compounds (i.e. less available charge for HOM and ON).

Neutral atom imaging at Mercury

NASA Astrophysics Data System (ADS)

Mura, A.; Orsini, S.; Milillo, A.; Di Lellis, A. M.; De Angelis, E.

2006-02-01

The feasibility of neutral atom detection and imaging in the Hermean environment is discussed in this study. In particular, we consider those energetic neutral atoms (ENA) whose emission is directly related to solar wind entrance into Mercury's magnetosphere. In fact, this environment is characterised by a weak magnetic field; thus, cusp regions are extremely large if compared to the Earth's ones, and intense proton fluxes are expected there. Our study includes a model of H + distribution in space, energy and pitch angle, simulated by means of a single-particle, Monte-Carlo simulation. Among processes that could generate neutral atom emission, we focus our attention on charge-exchange and ion sputtering, which, in principle, are able to produce directional ENA fluxes. Simulated neutral atom images are investigated in the frame of the neutral particle analyser-ion spectrometer (NPA-IS) SERENA experiment, proposed to fly on board the ESA mission BepiColombo/MPO. The ELENA (emitted low-energy neutral atoms) unit, which is part of this experiment, will be able to detect such fluxes; instrumental details and predicted count rates are given.

Fullerene ion chemistry: a journey of discovery and achievement

PubMed Central

Böhme, Diethard K.

2016-01-01

An account is provided of the extraordinary features of buckminster fullerene cations and their chemistry that we discovered in our Ion Chemistry Laboratory at York University (Canada) during a ‘golden’ period of research in the early 1990s, just after C60 powder became available. We identified new chemical ways of C60 ionization and tracked novel chemistry of C60n+ as a function of charge state (n=1–3) with some 50 different reagent molecules. We found that multiple charges enhance reaction rates and diversify reaction products and mechanisms. Strong electrostatic interactions with reagent molecules were seen to reduce barriers to carbon surface bonding and charge-separation reactions, while intramolecular Coulomb repulsion appeared to localize charge on the surface or the substituent and so influence higher order chemistry, including ‘spindle’, ‘star’, ‘fuzzy ball’, ‘ball-and-chain’ and dimer ion formation. We introduced the notion of ‘apparent’ gas-phase acidity with measurements of proton-transfer reactions of multiply charged fullerene cations. We also explored the attachment of atomic metal cations to C60 and their subsequent reactions. All these findings were applied to the possible chemistry of fullerene cations in the interstellar medium with a focus on multiply charged fullerene ion formation and the intervention of fullerene cations in fullerene derivatization and molecular synthesis, with a view to their possible future detection. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’. PMID:27501972

Electron stimulated desorption of atomic oxygen from silver

NASA Technical Reports Server (NTRS)

Outlaw, R. A.; Peregoy, W. K.; Hoflund, Gar B.; Corallo, Gregory R.

1987-01-01

The electron stimulated desorption (ESD) of neutral oxygen atoms from polycrystalline silver and of oxygen ions from Ag(110) has been studied. Polycrystalline Ag charged with (16)O2 and (18)O2 and bombarded by low-energy electrons (approx 100 eV) under ultrahigh vacuum (UHV) conditions emitted O atom flux levels of 1 x 10 to the 12th power/sq cm/s at a Ag temperature of 300 C. The flux was detected with a quadrupole mass spectrometer operating in the appearance potential mode. The neutral cross section at about 100 C was determined to be 7 x 10 to the -19 sq cm. Ancillary experiments conducted in a UHV chamber equipped with a cylindrical mirror analyzer and rigged for ion energy distribution and ion angular distribution were used to study O ions desorbed from Ag(110). Two primary O(+) energies of 2.4 and 5.4 eV were detected from the Ag(110) after having been dosed with 2500 L of (16)O2. It also appears that in both experiments there was strong evidence for directionality of the emitted flux. The results of this study serve as a proof of concept for the development of a laboratory atomic oxygen beam generator that simulates the gas flux environment experienced by orbiting vehicles.

Time-dependent Processes in the Sheath Between the Heliospheric Termination Shock and the Heliopause

NASA Astrophysics Data System (ADS)

Pogorelov, N. V.; Borovikov, S. N.; Heerikhuisen, J.; Kim, T. K.; Zank, G. P.

2014-09-01

In this paper, we present the results of our numerical simulation of the solar wind (SW) interaction with the local interstellar medium (LISM). In particular, a solar cycle model based on Ulysses measurements allowed us to estimate the interrelationship between heliospheric asymmetries due to the action of the interstellar magnetic field and the decrease in the solar wind ram pressure. We evaluate the possibility to develop an improved approach to derive SW boundary conditions from interplanetary scintillation data. It is shown that solar cycle affects stability of the heliopause in a way favorable for the interpretation of Voyager 1 “early” penetration into the local interstellar medium. We also show that the heliotail is always a subject of violent Kelvin-Helmholtz instability, which ultimately should make the heliotail indistinguishable from the LISM. Numerical results are obtained with a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), which is a package of numerical codes capable of performing adaptive mesh refinement simulations of complex plasma flows in the presence of discontinuities and charge exchange between ions and neutral atoms. The flow of the ionized component is described with the ideal MHD equations, while the transport of atoms is governed either by the Boltzmann equation or multiple Euler gas dynamics equations. We have enhanced the code with additional physical treatments for the transport of turbulence and acceleration of pickup ions in interplanetary space and at the termination shock.

Theoretical investigation on the soft X-ray spectrum of the highly-charged W54+ ions

NASA Astrophysics Data System (ADS)

Ding, Xiaobin; Yang, Jiaoxia; Koike, Fumihiro; Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A.; Nakamura, Nobuyuki; Dong, Chenzhong

2018-01-01

A detailed level collisional-radiative model of the E1 transition spectrum of Ca-like W54+ ion has been constructed. All the necessary atomic data has been calculated by relativistic configuration interaction (RCI) method with the implementation of Flexible Atomic Code (FAC). The results are in reasonable agreement with the available experimental and previous theoretical data. The synthetic spectrum has explained the EBIT spectrum in 29.5-32.5 Å , while several new strong transitions has been predicted to be observed in 18.5-19.6 Å for the future EBIT experiment with electron density ne = 1012 cm-3 and electron beam energy Ee = 18.2 keV.

Measurements of neutral and ion velocity distribution functions in a Hall thruster

NASA Astrophysics Data System (ADS)

Svarnas, Panagiotis; Romadanov, Iavn; Diallo, Ahmed; Raitses, Yevgeny

2015-11-01

Hall thruster is a plasma device for space propulsion. It utilizes a cross-field discharge to generate a partially ionized weakly collisional plasma with magnetized electrons and non-magnetized ions. The ions are accelerated by the electric field to produce the thrust. There is a relatively large number of studies devoted to characterization of accelerated ions, including measurements of ion velocity distribution function using laser-induced fluorescence diagnostic. Interactions of these accelerated ions with neutral atoms in the thruster and the thruster plume is a subject of on-going studies, which require combined monitoring of ion and neutral velocity distributions. Herein, laser-induced fluorescence technique has been employed to study neutral and single-charged ion velocity distribution functions in a 200 W cylindrical Hall thruster operating with xenon propellant. An optical system is installed in the vacuum chamber enabling spatially resolved axial velocity measurements. The fluorescence signals are well separated from the plasma background emission by modulating the laser beam and using lock-in detectors. Measured velocity distribution functions of neutral atoms and ions at different operating parameters of the thruster are reported and analyzed. This work was supported by DOE contract DE-AC02-09CH11466.

Negative ion and dust grain charge in Titan's ionosphere: multi-instrument case study

NASA Astrophysics Data System (ADS)

Shebanits, O.; Wahlund, J.-E.; Edberg, N. J. T.; Wellbrock, A.; Coates, A. J.; Crary, F.; Andrews, D.

2014-04-01

The Cassini s/c in-situ plasma measurements of Titan's ionosphere by Radio and Plasma Wave Science (RPWS) Langmuir Probe (LP), Cassini Plasma Spectrometer (CAPS) Electron (ELS) and Ion Beam (IBS) spectrometers are combined for selected flybys (T16, T20, T29, T40 and T56) to further constrain plasma parameters of ionosphere below 1400 km.

A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sigaud, L., E-mail: lsigaud@if.uff.br; Jesus, V. L. B. de; Ferreira, Natalia

In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell—to study ionization of atoms and molecules by electron impact—is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements.

PubMed

Sigaud, L; de Jesus, V L B; Ferreira, Natalia; Montenegro, E C

2016-08-01

In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell-to study ionization of atoms and molecules by electron impact-is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

IBIC characterisation of novel detectors for single atom doping of quantum computer devices

NASA Astrophysics Data System (ADS)

Yang, Changyi; Jamieson, David N.; Pakes, Chris I.; George, Damien P.; Hearne, Sean M.; Dzurak, Andrew S.; Gauja, Eric; Stanley, F.; Clark, R. G.

2003-09-01

Single ion implantation and online detection is highly desirable for the emerging application, in which single 31P ions need to be inserted in prefabricated silicon cells to construct solid-state quantum bits (qubits). In order to fabricate qubit arrays, we have developed novel detectors that employ detector electrodes adjacent to the prefabricated cells that can detect single keV ion strikes appropriate for the fabrication of shallow phosphorus arrays. The method utilises a high purity silicon substrate with very high resistivity, a thin SiO 2 surface layer, nanometer masks for the lateral positioning single phosphorus implantation, biased electrodes applied to the surface of the silicon and sensitive electronics that can detect the charge transient from single keV ion strikes. A TCAD (Technology Computer Aided Design) software package was applied in the optimisation of the device design and simulation of the detector performance. Here we show the characterisation of these detectors using ion beam induced charge (IBIC) with a focused 2 MeV He ions in a nuclear microprobe. The IBIC imaging method in a nuclear microprobe allowed us to measure the dead-layer thickness of the detector structure (required to be very thin for successful detection of keV ions), and the spatial distribution of the charge collection efficiency around the entire region of the detector. We show that our detectors have near 100% charge collection efficiency for MeV ions, extremely thin dead-layer thickness (about 7 nm) and a wide active region extending laterally from the electrodes (10-20 μm) where qubit arrays can be constructed. We demonstrate that the device can be successfully applied in the detection of keV ionisation energy from single events of keV X-rays and keV 31P ions.

Oxygen Pickup Ions Measured by MAVEN Outside the Martian Bow Shock

NASA Astrophysics Data System (ADS)

Rahmati, A.; Cravens, T.; Larson, D. E.; Lillis, R. J.; Dunn, P.; Halekas, J. S.; Connerney, J. E. P.; Eparvier, F. G.; Thiemann, E.; Mitchell, D. L.; Jakosky, B. M.

2015-12-01

The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft entered orbit around Mars on September 21, 2014 and has since been detecting energetic oxygen pickup ions by its SEP (Solar Energetic Particles) and SWIA (Solar Wind Ion Analyzer) instruments. The oxygen pickup ions detected outside the Martian bowshock and in the upstream solar wind are associated with the extended hot oxygen exosphere of Mars, which is created mainly by the dissociative recombination of molecular oxygen ions with electrons in the ionosphere. We use analytic solutions to the equations of motion of pickup ions moving in the undisturbed upstream solar wind magnetic and motional electric fields and calculate the flux of oxygen pickup ions at the location of MAVEN. Our model calculates the ionization rate of oxygen atoms in the exosphere based on the hot oxygen densities predicted by Rahmati et al. (2014), and the sources of ionization include photo-ionization, charge exchange, and electron impact ionization. The photo-ionization frequency is calculated using the FISM (Flare Irradiance Spectral Model) solar flux model, based on MAVEN EUVM (Extreme Ultra-Violet Monitor) measurements. The frequency of charge exchange between a solar wind proton and an oxygen atom is calculated using MAVEN SWIA solar wind proton flux measurements, and the electron impact ionization frequency is calculated based on MAVEN SWEA (Solar Wind Electron Analyzer) solar wind electron flux measurements. The solar wind magnetic field used in the model is from the measurements taken by MAVEN MAG (magnetometer) in the upstream solar wind. The good agreement between our predicted pickup oxygen fluxes and the MAVEN SEP and SWIA measured ones confirms detection of oxygen pickup ions and these model-data comparisons can be used to constrain models of hot oxygen densities and photochemical escape flux.

Rotation driven translational diffusion of polyatomic ions in water: A novel mechanism for breakdown of Stokes-Einstein relation

NASA Astrophysics Data System (ADS)

Banerjee, Puja; Yashonath, Subramanian; Bagchi, Biman

2017-04-01

While most of the existing theoretical and simulation studies have focused on simple, spherical, halide and alkali ions, many chemically, biologically, and industrially relevant electrolytes involve complex non-spherical polyatomic ions like nitrate, chlorate, and sulfate to name only a few. Interestingly, some polyatomic ions in spite of being larger in size show anomalously high diffusivity and therefore cause a breakdown of the venerable Stokes-Einstein (S-E) relation between the size and diffusivity. Here we report a detailed analysis of the dynamics of anions in aqueous potassium nitrate (KNO3) and aqueous potassium acetate (CH3COOK) solutions. The two ions, nitrate (-NO3) and acetate (CH3-CO2 ), with their similar size show a large difference in diffusivity values. We present evidence that the translational motion of these polyatomic ions is coupled to the rotational motion of the ion. We show that unlike the acetate ion, nitrate ion with a symmetric charge distribution among all periphery oxygen atoms shows a faster rotational motion with large amplitude rotational jumps which enhances its translational motion due to translational-rotational coupling. By creating a family of modified-charge model systems, we have analysed the rotational motion of asymmetric polyatomic ions and the contribution of it to the translational motion. These model systems help clarifying and establishing the relative contribution of rotational motion in enhancing the diffusivity of the nitrate ion over the value predicted by the S-E relation and also over the other polyatomic ions having asymmetric charge distribution like the acetate ion. In the latter case, reduced rotational motion results in lower diffusivity values than those with symmetric charge distribution. We propose translational-rotational coupling as a general mechanism of the breakdown of the S-E relation in the case of polyatomic ions.

Rotation driven translational diffusion of polyatomic ions in water: A novel mechanism for breakdown of Stokes-Einstein relation.

PubMed

Banerjee, Puja; Yashonath, Subramanian; Bagchi, Biman

2017-04-28

While most of the existing theoretical and simulation studies have focused on simple, spherical, halide and alkali ions, many chemically, biologically, and industrially relevant electrolytes involve complex non-spherical polyatomic ions like nitrate, chlorate, and sulfate to name only a few. Interestingly, some polyatomic ions in spite of being larger in size show anomalously high diffusivity and therefore cause a breakdown of the venerable Stokes-Einstein (S-E) relation between the size and diffusivity. Here we report a detailed analysis of the dynamics of anions in aqueous potassium nitrate (KNO 3 ) and aqueous potassium acetate (CH 3 COOK) solutions. The two ions, nitrate (NO3-) and acetate (CH 3 CO2-), with their similar size show a large difference in diffusivity values. We present evidence that the translational motion of these polyatomic ions is coupled to the rotational motion of the ion. We show that unlike the acetate ion, nitrate ion with a symmetric charge distribution among all periphery oxygen atoms shows a faster rotational motion with large amplitude rotational jumps which enhances its translational motion due to translational-rotational coupling. By creating a family of modified-charge model systems, we have analysed the rotational motion of asymmetric polyatomic ions and the contribution of it to the translational motion. These model systems help clarifying and establishing the relative contribution of rotational motion in enhancing the diffusivity of the nitrate ion over the value predicted by the S-E relation and also over the other polyatomic ions having asymmetric charge distribution like the acetate ion. In the latter case, reduced rotational motion results in lower diffusivity values than those with symmetric charge distribution. We propose translational-rotational coupling as a general mechanism of the breakdown of the S-E relation in the case of polyatomic ions.

The response of the ionosphere to the injection of chemically reactive vapors

NASA Technical Reports Server (NTRS)

Bernhardt, P. A.

1976-01-01

As a gas released in the ionosphere expands, it is rapidly cooled. When the vapor becomes sufficiently tenuous, it is reheated by collisions with the ambient atmosphere and its flow is then governed by diffusive expansion. As the injected gas becomes well mixed with the plasma, a hole is created by chemical processes. In the case of diatomic hydrogen release, depression of the electron concentrations is governed by the charge exchange reaction between oxygen ions and hydrogen, producing positive hydroxyl ions. Hydroxyl ions rapidly react with the electron gas to produce excited oxygen and hydrogen atoms. Enhanced airglow emissions result from the transition of the excited atoms to lower energy states. The electron temperature in the depleted region rises sharply causing a thermal expansion of the plasma and a further reduction in the local plasma concentration.

AIE active multianalyte fluorescent probe for the detection of Cu2+, Ni2+ and Hg2+ ions.

PubMed

Pannipara, Mehboobali; Al-Sehemi, Abdullah G; Irfan, Ahmad; Assiri, Mohammed; Kalam, Abul; Al-Ammari, Yahya S

2018-08-05

A novel pyrazolyl chromene derivative (Probe 1) displaying aggregation induced emission (AIE) properties that capable of sensing of multiple metal ions has been designed and synthesized. The multi analyte probe exhibits selective sensing for Cu 2+ and Ni 2+ ions via fluorescence turn-off mechanism and ratiometric selectivity for Hg 2+ ions in aqueous media. The extent of binding of the probe with sensitive metal ions has been demonstrated. The experimental results were further investigated by computational means by optimizing the ground state geometries of Probe 1 and its various metal complexes for Probe 1-Ni, Probe 1-Hg and Probe 1-Cu using density functional theory (DFT) at B3LYP/6-31+g(d,p) (LANL2DZ) level. On the basis of binding energies, the stability of metal complexes has been studied. In Probe 1-Ni and Probe 1-Cu complexes, charge transfer has been observed from Probe 1 to metal ions revealing ligand to metal charge transfer (LMCT) while in Probe1-Hg complex LMCT as well as intra-molecular charge tranfer (ICT) within Probe 1. Copyright © 2018 Elsevier B.V. All rights reserved.

Singlet vs. triplet interelectronic repulsion in confined atoms

NASA Astrophysics Data System (ADS)

Sarsa, A.; Buendía, E.; Gálvez, F. J.; Katriel, J.

2018-06-01

Hund's multiplicity rule invariably holds for the ground configurations of few-electron atoms as well as those of multi-electron quantum dots. However, the ordering of the corresponding interelectronic repulsions exhibits a reversal in the former but not in the latter system, upon varying the system parameters. Here, we investigate the transition between these two types of behaviour by studying few-electron atoms confined in spherical cavities. "Counter-intuitive" ordering of the interelectronic repulsions is confirmed when the nuclear charge is low enough and the cavity radius is large enough.

On the bosonic atoms

NASA Astrophysics Data System (ADS)

Amusia, M. Ya.; Chernysheva, L. V.

2018-01-01

We investigate ground state properties of atoms, in which substitute fermions - electrons by bosons, namely π --mesons. We perform some calculations in the frame of modified Hartree-Fock (HF) equation. The modification takes into account symmetry, instead of anti-symmetry of the pair identical bosons wave function. The modified HF approach thus enhances (doubles) the effect of self-action for the boson case. Therefore, we accordingly modify the HF equations by eliminating the self-action terms "by hand". The contribution of meson-meson and meson-nucleon non-Coulomb interaction is inessential at least for atoms with low and intermediate nuclear charge, which is our main subject. We found that the binding energy of pion negative ions A π - , pion atoms A π , and the number of extra bound pions ΔN π increases with the growth of nuclear charge Z. For e.g. Xe ΔN π = 4. As an example of a simple process with a pion atom, we consider photoionization that differs essentially from that for electron atoms. Namely, it is not monotonic decreasing from the threshold but has instead a prominent maximum above threshold. We study also elastic scattering of pions by pion atoms.

Multichordal charge exchange recombination spectroscopy on Doublet III (abstract)

NASA Astrophysics Data System (ADS)

Seraydarian, R. P.; Burrell, K. H.; Kahn, C.

1985-05-01

Single shot, multipoint ion temperature and plasma rotation profiles have been routinely obtained on the Doublet III tokamak for 32 consecutive time slices with 20-ms resolution. A six-chord tangentially viewing spectroscopic diagnostic has been built to look at radiation emitted by fully stripped low-Z impurity ions (He, C, O) that have undergone charge exchange recombination with hydrogen atoms from a 3-MW heating beam. The main components of the instrument are a single monochromator for wavelength dispersion, a single image intensifier tube for photon gain, and a pair of 1024-element linear photodiode arrays for detection. A special arrangement of fiber optics allows simultaneous data acquisition from all chords without the use of scanning mirrors or other moving parts. Ion temperature profiles taken under a variety of plasma conditions will be presented.

Understanding the impact of the central atom on the ionic liquid behavior: phosphonium vs ammonium cations.

PubMed

Carvalho, Pedro J; Ventura, Sónia P M; Batista, Marta L S; Schröder, Bernd; Gonçalves, Fernando; Esperança, José; Mutelet, Fabrice; Coutinho, João A P

2014-02-14

The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.

Understanding the impact of the central atom on the ionic liquid behavior: Phosphonium vs ammonium cations

NASA Astrophysics Data System (ADS)

Carvalho, Pedro J.; Ventura, Sónia P. M.; Batista, Marta L. S.; Schröder, Bernd; Gonçalves, Fernando; Esperança, José; Mutelet, Fabrice; Coutinho, João A. P.

2014-02-01

The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.

Stability of the magnetosonic wave in a cometary multi-ion plasma

NASA Astrophysics Data System (ADS)

Sreekala, G.; Varghese, Anu; Jayakumar, Neethu; Michael, Manesh; Sebastian, Sijo; Venugopal, Chandu

2017-05-01

A generalized dispersion relation of the magnetosonic wave in a four component plasma consisting of electrons and hydrogen ions of solar origin and positively and negatively charged oxygen ions of cometary origin has been derived by using the Vlasov-Maxwell kinetic model. Parallel to the magnetic field, the hydrogen and electron components are modeled by a drifting Maxwellian distribution; perpendicular to the magnetic field, we use a loss cone type distribution obtained by the subtraction of two Maxwellian distributions having different temperatures. The effect of change in the drift velocity of streaming components and number densities and temperatures of each species in driving the instability has been analyzed both analytically and numerically. For typical parameters at comet Halley, we find that both positively and negatively charged oxygen ions can drive the wave unstable.

Model Based Optimal Control, Estimation, and Validation of Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Perez, Hector Eduardo

This dissertation focuses on developing and experimentally validating model based control techniques to enhance the operation of lithium ion batteries, safely. An overview of the contributions to address the challenges that arise are provided below. Chapter 1: This chapter provides an introduction to battery fundamentals, models, and control and estimation techniques. Additionally, it provides motivation for the contributions of this dissertation. Chapter 2: This chapter examines reference governor (RG) methods for satisfying state constraints in Li-ion batteries. Mathematically, these constraints are formulated from a first principles electrochemical model. Consequently, the constraints explicitly model specific degradation mechanisms, such as lithium plating, lithium depletion, and overheating. This contrasts with the present paradigm of limiting measured voltage, current, and/or temperature. The critical challenges, however, are that (i) the electrochemical states evolve according to a system of nonlinear partial differential equations, and (ii) the states are not physically measurable. Assuming available state and parameter estimates, this chapter develops RGs for electrochemical battery models. The results demonstrate how electrochemical model state information can be utilized to ensure safe operation, while simultaneously enhancing energy capacity, power, and charge speeds in Li-ion batteries. Chapter 3: Complex multi-partial differential equation (PDE) electrochemical battery models are characterized by parameters that are often difficult to measure or identify. This parametric uncertainty influences the state estimates of electrochemical model-based observers for applications such as state-of-charge (SOC) estimation. This chapter develops two sensitivity-based interval observers that map bounded parameter uncertainty to state estimation intervals, within the context of electrochemical PDE models and SOC estimation. Theoretically, this chapter extends the notion of interval observers to PDE models using a sensitivity-based approach. Practically, this chapter quantifies the sensitivity of battery state estimates to parameter variations, enabling robust battery management schemes. The effectiveness of the proposed sensitivity-based interval observers is verified via a numerical study for the range of uncertain parameters. Chapter 4: This chapter seeks to derive insight on battery charging control using electrochemistry models. Directly using full order complex multi-partial differential equation (PDE) electrochemical battery models is difficult and sometimes impossible to implement. This chapter develops an approach for obtaining optimal charge control schemes, while ensuring safety through constraint satisfaction. An optimal charge control problem is mathematically formulated via a coupled reduced order electrochemical-thermal model which conserves key electrochemical and thermal state information. The Legendre-Gauss-Radau (LGR) pseudo-spectral method with adaptive multi-mesh-interval collocation is employed to solve the resulting nonlinear multi-state optimal control problem. Minimum time charge protocols are analyzed in detail subject to solid and electrolyte phase concentration constraints, as well as temperature constraints. The optimization scheme is examined using different input current bounds, and an insight on battery design for fast charging is provided. Experimental results are provided to compare the tradeoffs between an electrochemical-thermal model based optimal charge protocol and a traditional charge protocol. Chapter 5: Fast and safe charging protocols are crucial for enhancing the practicality of batteries, especially for mobile applications such as smartphones and electric vehicles. This chapter proposes an innovative approach to devising optimally health-conscious fast-safe charge protocols. A multi-objective optimal control problem is mathematically formulated via a coupled electro-thermal-aging battery model, where electrical and aging sub-models depend upon the core temperature captured by a two-state thermal sub-model. The Legendre-Gauss-Radau (LGR) pseudo-spectral method with adaptive multi-mesh-interval collocation is employed to solve the resulting highly nonlinear six-state optimal control problem. Charge time and health degradation are therefore optimally traded off, subject to both electrical and thermal constraints. Minimum-time, minimum-aging, and balanced charge scenarios are examined in detail. Sensitivities to the upper voltage bound, ambient temperature, and cooling convection resistance are investigated as well. Experimental results are provided to compare the tradeoffs between a balanced and traditional charge protocol. Chapter 6: This chapter provides concluding remarks on the findings of this dissertation and a discussion of future work.

3D tomographic reconstruction of the terrestrial exosphere and its time-dependent coupling to the magnetospheric ring current

NASA Astrophysics Data System (ADS)

Waldrop, L.; Cucho-Padin, G.; Ilie, R.

2017-12-01

Charge exchange collisions between ring current ions and hydrogen (H) atoms in the outer exosphere serve to dissipate magnetospheric energy, particularly during the slow recovery phase of geomagnetic storms, through the generation of energetic neutral atoms (ENAs) which escape the system. As a result, knowledge of the spatial distribution and temporal variability of exospheric H density is critical for reliable interpretation of ENA flux measurements as well as for accurate modeling of the ring current. Although numerous theoretical, numerical, and empirical H distributions have been used for such analyses, their reliance on ad hoc or unphysical assumptions, together with their inherently static formulations, is a source of significant uncertainty. Our recent development of a robust tomographic technique for the model-independent estimation of global exospheric H density from optical remote sensing data overcomes the limitations of past analysis and enables an unprecedented investigation of global exospheric and ring current dynamics. Here, we present sample results of our 3D, time-dependent reconstructions of exospheric structure, derived from measurements of resonantly scattered solar Lyman-alpha (121.6 nm) photons acquired by the Lyman-alpha detectors (LADs) onboard NASA's Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission. We use the Hot Electron and Ion Drift Integrator (HEIDI) kinetic model of the ring current to investigate the charge exchange interactions between the resulting H density distribution and ring current ions and generate synthetic images of ENA flux for comparison with those measured by TWINS.

Silicon as a model ion trap: Time domain measurements of donor Rydberg states

PubMed Central

Vinh, N. Q.; Greenland, P. T.; Litvinenko, K.; Redlich, B.; van der Meer, A. F. G.; Lynch, S. A.; Warner, M.; Stoneham, A. M.; Aeppli, G.; Paul, D. J.; Pidgeon, C. R.; Murdin, B. N.

2008-01-01

One of the great successes of quantum physics is the description of the long-lived Rydberg states of atoms and ions. The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual Bohr–Sommerfeld formula, shifted to the far-infrared because of the small effective mass and high dielectric constant. Manipulation of Rydberg states in free atoms and ions by single and multiphoton processes has been tremendously productive since the development of pulsed visible laser spectroscopy. The analogous manipulations have not been conducted for donor impurities in silicon. Here, we use the FELIX pulsed free electron laser to perform time-domain measurements of the Rydberg state dynamics in phosphorus- and arsenic-doped silicon and we have obtained lifetimes consistent with frequency domain linewidths for isotopically purified silicon. This implies that the dominant decoherence mechanism for excited Rydberg states is lifetime broadening, just as for atoms in ion traps. The experiments are important because they represent a step toward coherent control and manipulation of atomic-like quantum levels in the most common semiconductor and complement magnetic resonance experiments in the literature, which show extraordinarily long spin lattice relaxation times—key to many well known schemes for quantum computing qubits—for the same impurities. Our results, taken together with the magnetic resonance data and progress in precise placement of single impurities, suggest that doped silicon, the basis for modern microelectronics, is also a model ion trap.

On the size and structure of helium snowballs formed around charged atoms and clusters of noble gases.

PubMed

Bartl, Peter; Leidlmair, Christian; Denifl, Stephan; Scheier, Paul; Echt, Olof

2014-09-18

Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. HenNgx(+) ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He20(84)Kr2(+) and the isobaric, nonmagic He41(84)Kr(+). Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for HenAr(+), which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for HenNa(+) [J. Phys. Chem. A 2011, 115, 7300] that reveal three shells of icosahedral symmetry. HenArx(+) (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of HenKrx(+) suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr(+) to Kr3(+). Previously reported strong anomalies at He12Kr2(+) and He12Kr3(+) [Kim , J. H.; et al. J. Chem. Phys. 2006, 124, 214301] are attributed to a contamination. Only minor local anomalies appear in the distributions of HenXex(+) (x ≤ 3). The distributions of HenKr(+) and HenXe(+) show strikingly similar, broad features that are absent from the distribution of HenAr(+); differences are tentatively ascribed to the very different fragmentation dynamics of these ions.

On the Size and Structure of Helium Snowballs Formed around Charged Atoms and Clusters of Noble Gases

PubMed Central

2013-01-01

Helium nanodroplets doped with argon, krypton, or xenon are ionized by electrons and analyzed in a mass spectrometer. HenNgx+ ions containing up to seven noble gas (Ng) atoms and dozens of helium atoms are identified; the high resolution of the mass spectrometer combined with advanced data analysis make it possible to unscramble contributions from isotopologues that have the same nominal mass but different numbers of helium or Ng atoms, such as the magic He2084Kr2+ and the isobaric, nonmagic He4184Kr+. Anomalies in these ion abundances reveal particularly stable ions; several intriguing patterns emerge. Perhaps most astounding are the results for HenAr+, which show evidence for three distinct, solid-like solvation shells containing 12, 20, and 12 helium atoms. This observation runs counter to the common notion that only the first solvation shell is solid-like but agrees with calculations by Galli et al. for HenNa+ [J. Phys. Chem. A2011, 115, 730021568337] that reveal three shells of icosahedral symmetry. HenArx+ (2 ≤ x ≤ 7) ions appear to be especially stable if they contain a total of n + x = 19 atoms. A sequence of anomalies in the abundance distribution of HenKrx+ suggests that rings of six helium atoms are inserted into the solvation shell each time a krypton atom is added to the ionic core, from Kr+ to Kr3+. Previously reported strong anomalies at He12Kr2+ and He12Kr3+ [KimJ. H.; et al. J. Chem. Phys.2006, 124, 21430116774401] are attributed to a contamination. Only minor local anomalies appear in the distributions of HenXex+ (x ≤ 3). The distributions of HenKr+ and HenXe+ show strikingly similar, broad features that are absent from the distribution of HenAr+; differences are tentatively ascribed to the very different fragmentation dynamics of these ions. PMID:24128371

On charge exchange and knock-on processes in the exosphere of Io

NASA Technical Reports Server (NTRS)

Ip, W.-H.

1982-01-01

One direct consequence of magnetospheric interaction of Io is the strong dynamical coupling of its neutral atmosphere with the corotating plasma. The absorption of the thermal ions and the associated neutral injection is an improtant issue not yet explored. As far as nonthermal escape of the neutral atmosphere is concerned, three processes stand out. That is, apart from sputtering, exospheric interactions like atom-ion knock-on collision and charge exchange recombination could be a significant source of the neutral clouds in the Jovian system. Using a current electrodynamic model of Io, both the absorption rate of the corotating thermal plasma and the production rates of new exospheric ions and the fast neutrals are considered. It is found that the source strength of the neutral atoms and molecules with speeds of about 100 km/sec could amount to 10 to the 26th/sec whereas exospheric neutrals emitted at lower speed (of about 10 km/sec) amounts to 4 x 10 to the 25th/sec. The generation of the new ions in connection with the streaming of the magnetospheric plasma around Io could also produce an asymmetric sputtering with a neutral flux of about 10 to the 27th/sec emitted from the region of Io which faces Jupiter. These results may be related to a number of sodium observations.

Applications of high-energy heavy-ions from superconducting cyclotrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimm, T. L.

1999-06-10

The superconducting cyclotrons of the National Superconducting Cyclotron Laboratory (NSCL), a major nuclear physics facility, can provide ions of any element from hydrogen to uranium. A major upgrade to the NSCL is underway and will consist of an electron cyclotron resonance (ECR) ion source followed by two large superconducting cyclotrons (K500 and K1200). Ions can be extracted at any point along this chain allowing a large range of energies and charge states. The ion energies range from a few keV to over 20 GeV, and charge states up to fully stripped {sup 197}Au{sup 79+} and two electron {sup 238}U{sup 90+}more » are possible. The long range of the high-energy heavy-ions allows them to penetrate deeply into a target that is placed in air, outside a vacuum chamber. The ion beams have already been used for a number of applications including; ion implantation, atomic physics, single event effects in integrated circuits, DNA radiation studies, radiation detector studies, flux pinning in high-T{sub c} superconductors, calibration of a space-based spectrometer, isotropic ratio measurements, material wear studies, and continuous positron emission tomography imaging.« less

Making the invisible visible: improved electrospray ion formation of metalloporphyrins/-phthalocyanines by attachment of the formate anion (HCOO(-)).

PubMed

Hitzenberger, Jakob Felix; Dammann, Claudia; Lang, Nina; Lungerich, Dominik; García-Iglesias, Miguel; Bottari, Giovanni; Torres, Tomás; Jux, Norbert; Drewello, Thomas

2016-02-21

A protocol is developed for the coordination of the formate anion (HCOO(-)) to neutral metalloporphyrins (Pors) and -phthalocyanines (Pcs) containing divalent metals as a means to improve their ion formation in electrospray ionization (ESI). This method is particularly useful when the oxidation of the neutral metallomacrocycle fails. While focusing on Zn(II)Pors and Zn(II)Pcs, we show that formate is also readily attached to Mn(II), Mg(II) and Co(II)Pcs. However, for the Co(II)Pc secondary reactions can be observed. Upon collision-induced dissociation (CID), Zn(II)Por/Pc·formate supramolecular complexes can undergo the loss of CO2 in combination with transfer of a hydride anion (H(-)) to the zinc metal center. Further dissociation leads to electron transfer and hydrogen atom loss, generating a route to the radical anion of the Zn(II)Por/Pc without the need for electrochemical reduction, although the Zn(II)Por/Pc may have a too low electron affinity to allow electron transfer directly from the formate anion. In addition to single Por molecules, multi Por arrays were successfully analyzed by this method. In this case, multiple addition of formate occurs, giving rise to multiply charged species. In these multi Por arrays, complexation of the formate anion occurs by two surrounding Por units (sandwich). Therefore, the maximum attainment of formate anions in these arrays corresponds to the number of such sandwich complexes rather than the number of porphyrin moieties. The same bonding motif leads to dimers of the composition [(Zn(II)Por/Pc)2·HCOO](-). In these, the formate anion can act as a structural probe, allowing the distinction of isomeric ions with the formate bridging two macrocycles or being attached to a dimer of directly connected macrocycles.

Low frequency vibrational spectra and the nature of metal-oxygen bond of alkaline earth metal acetylacetonates

NASA Astrophysics Data System (ADS)

Fakheri, Hamideh; Tayyari, Sayyed Faramarz; Heravi, Mohammad Momen; Morsali, Ali

2017-12-01

Theoretical quantum chemistry calculations were used to assign the observed vibrational band frequencies of Be, Mg, Ca, Sr, and Ba acetylacetonates complexes. Density functional theory (DFT) calculations have been carried out at the B3LYP level, using LanL2DZ, def2SVP, and mixed, GenECP, (def2SVP for metal ions and 6-311++G** for all other atoms) basis sets. The B3LYP level, with mixed basis sets, was utilized for calculations of vibrational frequencies, IR intensity, and Raman activity. Analysis of the vibrational spectra indicates that there are several bands which could almost be assigned mainly to the metal-oxygen vibrations. The strongest Raman band in this region could be used as a measure of the stability of the complex. The effects of central metal on the bond orders and charge distributions in alkaline earth metal acetylacetonates were studied by the Natural Bond Orbital (NBO) method for fully optimized compounds. Optimization were performed at the B3LYP/6-311++G** level for the lighter alkaline earth metal complexes (Be, Mg, and Ca acetylacetonates) while the B3LYP level, using LanL2DZ (extrabasis, d and f on oxygen and metal atoms), def2SVP and mixed (def2SVP on metal ions and 6-311++G** for all other atoms) basis sets for all understudy complexes. Calculations indicate that the covalence nature of metal-oxygen bonds considerably decreases from Be to Ba complexes. The nature of metal-oxygen bond was further studied by using Atoms In Molecules (AIM) analysis. The topological parameters, Wiberg bond orders, natural charges of O and metal ions, and also some vibrational band frequencies were correlated with the stability constants of understudy complexes.

Secondary Interstellar Oxygen in the Heliosphere: Numerical Modeling and Comparison with IBEX-Lo Data

NASA Astrophysics Data System (ADS)

Baliukin, I. I.; Izmodenov, V. V.; Möbius, E.; Alexashov, D. B.; Katushkina, O. A.; Kucharek, H.

2017-12-01

Quantitative analysis of the interstellar heavy (oxygen and neon) atom fluxes obtained by the Interstellar Boundary Explorer (IBEX) suggests the existence of the secondary interstellar oxygen component. This component is formed near the heliopause due to charge exchange of interstellar oxygen ions with hydrogen atoms, as was predicted theoretically. A detailed quantitative analysis of the fluxes of interstellar heavy atoms is only possible with a model that takes into account both the filtration of primary and the production of secondary interstellar oxygen in the boundary region of the heliosphere as well as a detailed simulation of the motion of interstellar atoms inside the heliosphere. This simulation must take into account photoionization, charge exchange with the protons of the solar wind and solar gravitational attraction. This paper presents the results of modeling interstellar oxygen and neon atoms through the heliospheric interface and inside the heliosphere based on a three-dimensional kinetic-MHD model of the solar wind interaction with the local interstellar medium and a comparison of these results with the data obtained on the IBEX spacecraft.

Electron capture in collisions of S4+ with atomic hydrogen

NASA Astrophysics Data System (ADS)

Stancil, P. C.; Turner, A. R.; Cooper, D. L.; Schultz, D. R.; Rakovic, M. J.; Fritsch, W.; Zygelman, B.

2001-06-01

Charge transfer processes due to collisions of ground state S4+(3s2 1S) ions with atomic hydrogen are investigated for energies between 1 meV u-1 and 10 MeV u-1 using the quantum mechanical molecular-orbital close-coupling (MOCC), atomic-orbital close-coupling, classical trajectory Monte Carlo (CTMC) and continuum distorted wave methods. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial coupling matrix elements obtained with the spin-coupled valence-bond approach. A number of variants of the CTMC approach were explored, including different momentum and radial distributions for the initial state, as well as effective charge and quantum-defect models to determine the corresponding quantum state after capture into final partially stripped S3+ excited classical states. Hydrogen target isotope effects are explored and rate coefficients for temperatures between 100 and 106 K are also presented.

Electron quantum dynamics in atom-ion interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabzyan, H., E-mail: sabzyan@sci.ui.ac.ir; Jenabi, M. J.

2016-04-07

Electron transfer (ET) process and its dependence on the system parameters are investigated by solving two-dimensional time-dependent Schrödinger equation numerically using split operator technique. Evolution of the electron wavepacket occurs from the one-electron species hydrogen atom to another bare nucleus of charge Z > 1. This evolution is quantified by partitioning the simulation box and defining regional densities belonging to the two nuclei of the system. It is found that the functional form of the time-variations of these regional densities and the extent of ET process depend strongly on the inter-nuclear distance and relative values of the nuclear charges, whichmore » define the potential energy surface governing the electron wavepacket evolution. Also, the initial electronic state of the single-electron atom has critical effect on this evolution and its consequent (partial) electron transfer depending on its spreading extent and orientation with respect to the inter-nuclear axis.« less

Experiments with trapped ions and ultrafast laser pulses

NASA Astrophysics Data System (ADS)

Johnson, Kale Gifford

Since the dawn of quantum information science, laser-cooled trapped atomic ions have been one of the most compelling systems for the physical realization of a quantum computer. By applying qubit state dependent forces to the ions, their collective motional modes can be used as a bus to realize entangling quantum gates. Ultrafast state-dependent kicks [1] can provide a universal set of quantum logic operations, in conjunction with ultrafast single qubit rotations [2], which uses only ultrafast laser pulses. This may present a clearer route to scaling a trapped ion processor [3]. In addition to the role that spin-dependent kicks (SDKs) play in quantum computation, their utility in fundamental quantum mechanics research is also apparent. In this thesis, we present a set of experiments which demonstrate some of the principle properties of SDKs including ion motion independence (we demonstrate single ion thermometry from the ground state to near room temperature and the largest Schrodinger cat state ever created in an oscillator), high speed operations (compared with conventional atom-laser interactions), and multi-qubit entanglement operations with speed that is not fundamentally limited by the trap oscillation frequency. We also present a method to provide higher stability in the radial mode ion oscillation frequencies of a linear radiofrequency (rf) Paul trap-a crucial factor when performing operations on the rf-sensitive modes. Finally, we present the highest atomic position sensitivity measurement of an isolated atom to date of 0.5 nm Hz. (-1/2) with a minimum uncertaintyof 1.7 nm using a 0.6 numerical aperature (NA) lens system, along with a method to correct aberrations and a direct position measurement of ion micromotion (the inherent oscillations of an ion trapped in an oscillating rf field). This development could be used to directly image atom motion in the quantum regime, along with sensing forces at the yoctonewton [10. (-24) N)] scale forgravity sensing, and 3D imaging of atoms from static to higher frequency motion. These ultrafast atomic qubit manipulation tools demonstrate inherent advantages over conventional techniques, offering a fundamentally distinct regime of control and speed not previously achievable.

Effect of atomic-scale defects and dopants on phosphorene electronic structure and quantum transport properties

DOE PAGES

Lopez-Bezanilla, Alejandro

2016-01-20

By means of a multi-scale first-principles approach, a description of the local electronic structure of 2D and narrow phosphorene sheets with various types of modifications is presented. Firtly, a rational argument based on the geometry of the pristine and modified P network, and supported by the Wannier functions formalism is introduced to describe a hybridization model of the P atomic orbitals. Ab initio calculations show that non-isoelectronic foreign atoms form quasi-bound states at varying energy levels and create different polarization states depending on the number of valence electrons between P and the doping atom. The quantum transport properties of modifiedmore » phosphorene ribbons are further described with great accuracy. The distortions on the electronic bands induced by the external species lead to strong backscattering effects on the propagating charge carriers. Depending on the energy of the charge carrier and the type of doping, the conduction may range from the diffusive to the localized regime. Interstitial defects at vacant sites lead to homogeneous transport fingerprints across different types of doping atoms. We suggest that the relatively low values of charge mobility reported in experimental measurements may have its origin in the presence of defects.« less

Structure of alcohol cluster ions in the gas phase, according to spectrometry and ab initio calculations

NASA Astrophysics Data System (ADS)

Krisilov, A. V.; Lantsuzskaya, E. V.; Levina, A. M.

2017-01-01

Reduced ion mobility and scattering cross sections are calculated from experimentally obtained spectra of the ion mobility of linear aliphatic alcohols with carbon atom numbers from 2 to 9. A linear increase in the scattering cross sections as the molecular weight grows is found. According to the results from experiments and quantum chemical calculations, alcohol cluster ions do not form a compact structure. Neither are dipole moments compensated for during dimerization, in contrast to the aldehydes and ketones described earlier. It was concluded from ab initio calculations that charge delocalization in monomeric and dimeric ions of alcohols increases the dipole moment many times over.

High Resolution X-ray Measurements Following Charge Exchange with Atomic H: Data for a New Observational Window on Diffuse Astrophysical Sources

NASA Astrophysics Data System (ADS)

Havener, Charles

It is rapidly being realized that many X-ray astronomical investigations are being affected in one way or another by charge exchange emission. Metal abundance measurements in supernova remnants and in outflows from star-forming galaxies need to be corrected for this additional process, and all X-ray observations of low surface brightness objects, such as the outskirts of clusters, galactic halos, the intergalactic medium, and plasma emission from hot interstellar gas are seriously compromised by a highly variable and largely unpredictable foreground from the exchange of solar wind ions on interstellar neutrals within the Solar system. At the same time, charge exchange provides a new sensitivity to mixing at interfaces between hot and cold gas, including direct measurements of relative velocities. The new generation of facilities with microcalorimeter detectors, starting with Astro-H in 2015, will provide the energy resolution and throughput for extended sources required to take advantage of this process. But analysis requires accurate partial cross sections for the production of individual lines, and even the most sophisticated of current charge exchange models do not do this with adequate precision. We propose an inexpensive modification of the Wisconsin high-throughput XQC microcalorimeter instrument so that it can be used on the merged beam facility at Oak Ridge to make direct measurement of lines of interest from collisions between an assortment of heavy ions with neutral atomic hydrogen. In this beam-beam system, the entire range of astrophysically interesting relative velocities can be investigated. We will work closely with modelers to use these results to tune their models to give accurate results for additional ions.

Charge transfer in low-energy collisions of H with He+ and H+ with He in excited states

NASA Astrophysics Data System (ADS)

Loreau, J.; Ryabchenko, S.; Muñoz Burgos, J. M.; Vaeck, N.

2018-04-01

The charge transfer process in collisions of excited (n = 2, 3) hydrogen atoms with He+ and in collisions of excited helium atoms with H+ is studied theoretically. A combination of a fully quantum-mechanical method and a semi-classical approach is employed to calculate the charge-exchange cross sections at collision energies from 0.1 eV u‑1 up to 1 keV u‑1. These methods are based on accurate ab initio potential energy curves and non-adiabatic couplings for the molecular ion HeH+. Charge transfer can occur either in singlet or in triplet states, and the differences between the singlet and triplet spin manifolds are discussed. The dependence of the cross section on the quantum numbers n and l of the initial state is demonstrated. The isotope effect on the charge transfer cross sections, arising at low collision energy when H is substituted by D or T, is investigated. Rate coefficients are calculated for all isotopes up to 106 K. Finally, the impact of the present calculations on models of laboratory plasmas is discussed.

Mechanisms of dust grain charging in plasma with allowance for electron emission processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mol’kov, S. I.; Savin, V. N., E-mail: moped@onego.ru

2017-02-15

The process of dust grain charging is described with allowance for secondary, ion-induced, photoelectric, and thermal electron emission from the grain surface. The roughness of the grain surface is taken into account. An intermediate charging regime involving ion–atom collisions and electron ionization in the perturbed plasma region is analyzed using the moment equations and Poisson’s equation. A calculation method is proposed that allows one to take into account the influence of all the above effects and determine the radius of the plasma region perturbed by the dust grain.

The Response of the Ionospheric Cusp to the Solar Through Two Perspectives: Low Energy Changed Particle In-Situ Measurements and Low- Energy Neutral Atom Imaging

NASA Technical Reports Server (NTRS)

Coffey, V. N.; Moore, T. E.; Chandler, M. O.; Craven, P. D.

2000-01-01

The IMAGE mission provides a new perspective on the study of the response of the magnetosphere/ionosphere system to changing solar wind conditions, particularly the variability of ion outflow. Learning to interpret this new type of data becomes an essential step in the process of melding these results with the wealth of in-situ charged particle observations obtained over the past 25 years. In order to understand how the in-situ data correspond to and contrast with IMAGE results we will perform a conjunctive study of event data from two instruments to shed light on the coupling of the solar wind and ionosphere from these different perspectives. We will use the Low Energy Neutral Atom instrument (LENA) which images energetic neutral atom emissions from upward flowing ionospheric ions and the Thermal Ion Dynamics Instrument (TIDE) on the Polar satellite which measures in-situ ion outflow from 0.3-300 eV. Our primary goal will be to understand how comparing the imaging and in-situ perspectives can aid in the analysis of both data sets.

Investigation of the Contribution of Lower Charger State Ar Ions to the Unknown Faint X-Ray Feature Found in the Stacked Spectrum of Galaxy Clusters

NASA Astrophysics Data System (ADS)

Gall, Amy

Driven by the recent detection of an unidentified emission line previously reported at 3.55-3.57 keV in a stacked spectrum of galaxy clusters, in this work we investigated the resonant dielectronic recombination (DR) process in Li-like Ar as a possible source of, or contributor to, the emission line. The Li-like transition 1s22l-1s2l3l' was suggested to produce a 3.62 keV photon [1] near the unidentified line at 3.57 keV and was the primary focus of our study. The Electron Beam Ion Trap at NIST was used to produce and trap the highly-charged ions of argon. The energy of the quasi-monoenergetic electron beam was incremented in steps of 15 eV to scan over all of the Li-like Ar DR resonances. A Johann-type crystal spectrometer and a solid-state germanium detector were used to take x-ray measurements perpendicular to the electron beam. Our broadband results allowed us to identify the processes that produced specific spectral features, while our high-resolution spectra allowed the experimental separation of features that are less than 2 eV apart. We have used the collisional radiative model NOMAD [2] aided by atomic data calculations by FAC [3] to interpret our observations and account for corrections. Experimental results were compared to the atomic database AtomDB, used to fit the galaxy cluster spectra. We found a number of measured features due to DR in lower charge state Ar ions not included in the database, close in energy to the identified line at 3.57 keV, and suggest their inclusion for improved interpretation and diagnosis of other astrophysical spectra.

Mapping energetics of atom probe evaporation events through first principles calculations.

PubMed

Peralta, Joaquín; Broderick, Scott R; Rajan, Krishna

2013-09-01

The purpose of this work is to use atomistic modeling to determine accurate inputs into the atom probe tomography (APT) reconstruction process. One of these inputs is evaporation field; however, a challenge occurs because single ions and dimers have different evaporation fields. We have calculated the evaporation field of Al and Sc ions and Al-Al and Al-Sc dimers from an L1₂-Al₃Sc surface using ab initio calculations and with a high electric field applied to the surface. The evaporation field is defined as the electric field at which the energy barrier size is calculated as zero, corresponding to the minimum field that atoms from the surface can break their bonds and evaporate from the surface. The evaporation field of the surface atoms are ranked from least to greatest as: Al-Al dimer, Al ion, Sc ion, and Al-Sc dimer. The first principles results were compared with experimental data in the form of an ion evaporation map, which maps multi-ion evaporations. From the ion evaporation map of L1₂-Al₃Sc, we extract relative evaporation fields and identify that an Al-Al dimer has a lower evaporation field than an Al-Sc dimer. Additionally, comparatively an Al-Al surface dimer is more likely to evaporate as a dimer, while an Al-Sc surface dimer is more likely to evaporate as single ions. These conclusions from the experiment agree with the ab initio calculations, validating the use of this approach for modeling APT energetics. Copyright © 2013 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez-Bezanilla, Alejandro

By means of a multi-scale first-principles approach, a description of the local electronic structure of 2D and narrow phosphorene sheets with various types of modifications is presented. Firtly, a rational argument based on the geometry of the pristine and modified P network, and supported by the Wannier functions formalism is introduced to describe a hybridization model of the P atomic orbitals. Ab initio calculations show that non-isoelectronic foreign atoms form quasi-bound states at varying energy levels and create different polarization states depending on the number of valence electrons between P and the doping atom. The quantum transport properties of modifiedmore » phosphorene ribbons are further described with great accuracy. The distortions on the electronic bands induced by the external species lead to strong backscattering effects on the propagating charge carriers. Depending on the energy of the charge carrier and the type of doping, the conduction may range from the diffusive to the localized regime. Interstitial defects at vacant sites lead to homogeneous transport fingerprints across different types of doping atoms. We suggest that the relatively low values of charge mobility reported in experimental measurements may have its origin in the presence of defects.« less